Greenhouse Projects
Although building a greenhouse involves many of the same principles that go into building a larger structure, such as a house or a room addition, a greenhouse is a much simpler project. You can also choose to begin your greenhouse adventure with a modest unit, growing into a larger, more fully equipped version once you become familiar with the process of growing plants in a controlled, indoor environment.
The projects in this section will accommodate any need, whether you’re just starting out or looking to graduate to a much bigger, more complex greenhouse. Have a small yard and want to stick with the basics?
Regardless of which project you choose, keep in mind that it’s all about the plants. The greenhouse you build needs to serve the type of plants—and the stage of growth—you want for your garden. It must also be within your skills and energy to build, so you don’t wind up with a half-finished structure come summer.
In this chapter:
Custom Victorian Greenhouse
One objection to most kit greenhouses is that they tend to have little going for them on the style front: a plain metal framework supporting clear panels. If you’re looking for a greenhouse project that blends with the look and character of your home, your best bet is to design and build one yourself.
The custom greenhouse seen in this project is designed and scaled to fit lean-to-style against a south-facing wall on an 1890s-era Victorian house. The principal design details that make it blend are the kneewall, which uses the same narrow wood lapsiding as the house, and the custom windows and door, which feature an arch element that is also present in the house trim. At roughly 6 × 9 feet in floorplan, the greenhouse is on the small side. But a space-conserving built-in-bench helps the gardener who designed the greenhouse get maximum usage from this small space.
The glazing on the greenhouse is 1/4-inch-thick clear polycarbonate (See Resources). The roof panels are also clear 1/4-inch polycarbonate, but with a hollow twin-wall construction that resists shattering and limits condensation. The roof vents are operated by lift arms with integral thermometers. When the air temperature inside the greenhouse hits around 85 degrees, the vents pop open automatically. The windows and the door are custom-made by sandwiching polycarbonate panels between wood frames. To allow for movement of the materials, the frames are bolted together through oversized bolt holes. All but one of the windows are hinged on the tops so they can swing open to enhance ventilation.
The greenhouse seen here features a poured concrete slab that is set apart from the house by an isolation joint. The back wall studs and roof panels are not connected to the house either, thus the greenhouse is technically a freestanding structure. Gaps between the greenhouse and the house are covered with various flashings, each of which is connected to one of the structures only. This has several advantages: primarily, it allows the structure to move and shift slightly (thereby avoiding cracking of glazing and roof panels) as the soil conditions and temperature change. And if the structure is small enough and has adequate setback distance from your property lines, you likely will not need a building permit. If the greenhouse were connected to the house, you would be required to dig full frost footings, as well.
FRAMING
CUTTING LIST
KEY |
PART |
NO. |
DIMENSION |
MATERIAL |
A |
Post |
5 |
3 1/2 × 3 1/2 × 78" |
4 × 4 |
B |
Front/back plate |
2 |
1 1/2 × 3 1/2 × 84 1/2" |
PT 2 × 4 |
C |
End plate |
2 |
1 1/2 × 3 1/2 × 56" |
PT 2 × 4 |
D |
Door wall plate |
2 |
1 1/2 × 3 1/2 × 26" |
PT 2 × 4 |
E |
End cap-bottom |
2 |
1 1/2 × 3 1/2 × 63" |
2 × 4 |
F |
F/B cap-bottom |
2 |
1 1/2 × 3 1/2 × 84 1/2" |
2 × 4 |
G |
Back wall stud |
4 |
1 1/2 × 3 1/2 × 76 1/2" |
2 × 4 |
H |
Kneewall stud |
15 |
1 1/2 × 3 1/2 × 33” |
2 × 4 |
I |
Upper stud |
3 |
3 1/2 × 3 1/2 × 42” |
4 × 4 |
ROOF
CUTTING LIST
KEY |
PART |
NO. |
DIMENSION |
MATERIAL |
J |
End cap-top |
2 |
1 1/2 × 3 1/2 × 56" |
2 × 4 |
K |
F/B cap-top |
2 |
1 1/2 × 3 1/2 × 91 1/2" |
2 × 4 |
L |
Roof ridge |
1 |
1 1/2 × 3 1/2 × 64" |
2 × 4 |
M |
Skew rafter |
2 |
1 1/2 × 3 1/2 × 79" |
2 × 4 |
N |
Roof leg |
2 |
1 1/2 × 3 1/2 × 39 1/2" |
2 × 4 |
O |
Roof support |
5 |
1 1/2 × 3 1/2 × 34" |
2 × 4 |
P |
Rafter |
5 |
1 1/2 × 3 1/2 × 81" |
2 × 4 |
Q |
Cripple rafter |
2 |
1 1/2 × 3 1/2 × 30" |
2 × 4 |
R |
Cripple rafter |
2 |
1 1/2 × 3 1/2 × 22" |
2 × 4 |
S |
Cripple rafter |
2 |
1 1/2 × 3 1/2 × 12" |
2 × 4 |
T |
Roof panel-side |
2 |
1/4 × 42 × 63" |
Suntuf |
U |
Roof panel-main |
2 |
1/4 × 47 × 79" |
Suntuf |
WINDOW
CUTTING LIST (26 × 40 1/2")
KEY |
PART |
NO. |
DIMENSION |
MATERIAL |
W1 |
Rail-A |
2 |
3/4 × 3 1/2 × 26" |
1 × 4 |
W2 |
Stile-A |
2 |
3/4 × 3 1/2 × 33 1/2" |
1 × 4 |
W3 |
Rail-B |
2 |
3/4 × 3 1/2 × 19" |
1 × 4 |
W4 |
Stile-B |
2 |
3/4 × 3 1/2 × 40 1/2" |
1 × 4 |
W5 |
Insert |
2 |
3/4 × 5 1/4 × 19" |
1 × 4 |
W6 |
Glazing |
1 |
1/4 × 26 × 40 1/2" |
Palsun |
DOOR
CUTTING LIST (26 × 77 1/2")
KEY |
PART |
NO. |
DIMENSION |
MATERIAL |
D1 |
Rail-A |
1 |
3/4 × 3 1/2 × 26" |
1 × 4 |
D2 |
Rail-B |
1 |
3/4 × 5 1/2 × 26" |
1 × 6 |
D3 |
Rail-C |
1 |
3/4 × 3 1/2 × 19" |
1 × 4 |
D4 |
Rail-D |
1 |
3/4 × 5 1/2 × 19" |
1 × 6 |
D5 |
Stile-A |
2 |
3/4 × 3 1/2 × 68 1/2" |
1 × 4 |
D6 |
Stile-B |
2 |
3/4 × 5 1/2 × 77 1/2" |
1 × 4 |
D7 |
Insert |
16 |
3/4 × 5 1/2 × 7 3/4" |
1 × 6 |
D8 |
Glazing |
1 |
1/4 × 26 × 77 1/2" |
Palsun |
Materials for Building Custom Greenhouses
The glazing and roof panels in this custom greenhouse are made from 1/4"-thick polycarbonate panels. The roof panels have vertical walls and are hollow, which makes them more dimensionally stable and less likely to crack than clear panels (a big benefit for roof). The 1/4"-thick, clear polycarbonate used for the window and door glazing is very durable too. Standard 1/8"-thick clear acrylic can be used for roofs or glazing. It is relatively inexpensive and sold at most building centers. But it has a shorter lifespan than polycarbonate.
An automatic lifter arm contains a sensor that causes your roof window vents to raise when the interior temperature reaches a preset level—usually around 100°F.
Products for joining and fastening panels include a panel seam trim, which has wide flanges on both edges to accept two panels that butt together; 100% silicon caulk for sealing seams (check with the panel manufacturer for compatibility of adhesives and caulks); and rubber-gasket pole barn screws for fastening panels to rafters or purlins.
How to Build a Custom Victorian Greenhouse
Stake out the installation area for the greenhouse. Strip off vegetation and then excavate for the subbase material and that portion of the slab you want to be underground. For drainage reasons, plan your slab so at least 1 to 2" of the concrete is above grade.
Install a 4 to 6" thick layer of compactible gravel to create a stable subbase. Tamp the gravel with a hand tamper or rental compactor. The tamped surface should slope away from the house at a very shallow rate—about 1/16" per foot. Insert an isolation board strip (usually made of asphalt-impregnated fiberboard) between the slab area and the foundation wall to keep the structures separate.
Build the three-sided concrete form and position it on top of the subbase. Screw the three 2 × 4s together with deck screws and then tack a 1 × 4 or 2 × 4 across the top, back ends of the sides. Square and level the forms and then drive wood stakes outside the 2 × 4 members. Attach the form to the stakes with deck screws driven through the stakes and into the form boards.
NOTE: The slab seen here is sized so there is a concrete apron of 2 to 3" around the structure, resembling a foundation wall. Some builders prefer to size the slab so the corner posts are flush with the slab edges, allowing you to cover the gap at the concrete surface with siding.
Add reinforcement in the concrete area. For most DIYers, metal re-mesh is an easy reinforcement material to work with. It is sold in 5 × 50' rolls and in 4 × 8' sheets. Prop the re-mesh on some small stones or bolsters. The edges of the reinforcement should be at least 4 to 6" away from the sides, and no closer than 1" to the concrete surface.
Pour concrete into the form. For a slab of the dimensions shown (4" thick by 68 × 84") approximately 15 cu. ft. (1/2 yard) of concrete is required (thirty 60-pound bags of dry mix). Settle the concrete by rapping the forms lightly with a mallet, and then strike off the material before floating.
Set J-bolts into the concrete after it sets up and after you have rounded the edges with an edger tool. Make sure to follow your plan closely for the J-bolt positions. Cover the concrete with sheet plastic and allow it to dry overnight before removing the forms.
Install post anchors at the corners and at the doorjamb location. Standoff posts that elevate the post bottom slightly will greatly reduce the amount of water the post end will wick up from the footing.
Cut the 2 × 4 sill plates to fit between the posts, using pressure-treated lumber. Install the sill plates by fastening with a powder-actuated tool and concrete nails. Or, you can drill guide holes and install masonry anchor sleeves or simply drive concrete screws into the concrete.
Tack the posts in the standoff post bases with a couple of deck screws, making sure they are resting cleanly on the standoff pads. Also brace the posts with 2 × 4 braces so they are plumb. Tack all the posts in position and plumb them and then mark level cutting heights using a laser level or level for reference.
Remove the posts for trimming to final height, making sure to note which post belongs in which base. Marking and cutting in this manner ensures that the tops of all posts will be level even though the slab slopes away from the house. Precutting posts to the same length will result in a roof structure that is not flat. Reinstall the posts in the anchors and fasten with joist hanger nails or 16d galvanized nails.
Cut the 2 × 4 endwall cap plates to length and screw them to the tops of the corner posts with 3" deck screws. Test frequently to make sure the corners are square and the edges are flush with the post edges.
Clamp the doubled front and back wall cap plates together so the top plate overhangs the lower plate by 3 1/2" on each end. Screw the top plates to the endwall cap plates and then fasten the front and back wall plates together with 2 1/2" deck screws. Fasten the top cap plate on each end.
Build stud walls for the kneewalls between posts. Space the kneewall studs so they will be positioned beneath the intermediate posts. Attach cap plate to the tops of the studs.
Add 1 × 6 sills to the tops of the 2 × 4 kneewalls. The sills will cover the edges of the exterior siding, so make the interior edges flush with interior wall studs and cap plate.
Add intermediate 4 × 4 posts between the sills and the undersides of the doubled cap plates. These posts should be situated directly above kneewall studs. The posts are spaced so the distances between posts will create uniform-width bays for the windows.
Install back wall studs between the back sill plate and the back cap plates, spaced 16" on center. Do not attach these studs to the house—they must remain isolated from it structurally.
Construct and attach the roof ridge support wall, featuring a 2 × 6 on edge at the top of the wall. It is easiest to build this wall on the ground and then erect it as a unit. Use a pair of 2 × 4 braces to keep the support wall stable while you attach the rafters.
Position a 2 × 4 so it spans from the ridge pole and past the header. Transfer cutting lines onto the workpiece and then cut the outer support legs to length at the marked angle. Attach the legs with deck screws.
Cut the rafters. Set workpieces in position against the 2 × 6 ridge pole and mark the point where they meet the header. Make a birdsmouth cutout in each rafter so it will rest flush on the header (top photo). Cut a decorative profile on each rafter end according to the Diagram shown here (bottom photo).
Install the corner rafters. First, attach skew joist hangers to the ends of the ridge pole for the skewed rafters that extend out to the front corners. Nail the rafters into the hangers with joist hanger nails. Toenail them (or drive screws toenail style) to the header.
Fill in the remaining rafters. If you wish, you can use joist hanger hardware to attach the rafters to the ridge pole. Or, you can nail or screw them. Spacing between rafters should be uniform.
Measure from the corner rafters to the endwall headers to find the lengths for the side rafters in the hip wall configuration. Cut 2 × 4 workpieces to length for each rafter.
Clamp the side rafter workpieces to a sturdy worksurface and cut the top and bottom angles with a circular saw or jigsaw. The side rafters in this design do not overhang the wall headers. Attach the side rafters with screws driven through pilot holes.
Cut kneewall sheathing panels from exterior plywood and attach the panels to the kneewall studs with deck screws.
Cut and install trim boards and corner boards according to your plan for siding the kneewall. The tops of the trim boards should butt against the undersides of the sills.
Install the siding on the kneewall. Generally, it is a good idea to install siding that matches the house siding. However, a well-chosen contrasting material also can have a pleasing design impact.
Paint the structure prior to adding roof panels and windows with glazing. Two coats of exterior paint is an adequate finish for an exterior lumber product, such as this cedar siding. A base coat of primer is always a good idea.
Also seal the roof structure with paint before installing the roof panels. The charcoal colored paint seen here recalls the color of wrought iron, which was used frequently to construct greenhouses and related Victorian structures, such as orangeries.
Begin to fasten the roof panels. The twin-wall corrugated polycarbonate panels seen here are fastened directly to the rafters. A panel seaming strip with channels on each edge is fastened to the center rafter to create a transition between the two abutting panels. Install the strip first so you can take more accurate width measurements for cutting the panels.
Cut the first roof panel to rough size using a circular saw fitted with a fine-tooth panel-cutting blade. Use a straightedge cutting guide. Or, use a tablesaw if you have access to one.
Set one edge of the panel into the slot in the seam strip so it is in the exact position you’ll install it. Use a marking pen to trace a cutting line onto the panel, flush with the edge of the endwall. Remove the panel and cut it to size.
Set the panel into position and test the fit.
Fasten the roof panels with rubber-gasket equipped pole barn screws driven every 12" at each rafter or purlin. Take care not to overdrive the screws, but be sure they penetrate far enough to create a tight seal.
Cut the side roof panels to fit and attach them with rubber gasket screws. The hip seams will be covered with flashing (See here).
Frame openings for the roof vent cutouts. Install a pair of parallel framing members at the top and bottom of each opening. The tops of the frames should be flush against the roof panel.
Cut out the openings in the roof panels. Drill a starter hole at each corner and then use a drywall saw to make the cuts. Clean up the cut edges with sandpaper.
Install flashing over the hip roof seams. Here, common drip cap flashing is being fastened with rubber-gasket screws driven into the roof rafters.
Cover the gap between the standalone greenhouse structure and the house with metal flashing. Aluminum handy flashing (12" width) can be fastened to the house and lightly creased so it extends over the gap and forms a seal without any physical connection to the greenhouse.
Install roof vent covers. (Here, the installation of the covers was postponed to allow access through the vent holes for installing flashing.) Use a piano hinge to attach each roof vent cover to the roof.
Attach an automatic window vent opener to each roof vent cover, according to the hardware manufacturer’s instructions. These devices have internal sensors that lift the vent cover when the greenhouse overheats.
Make the greenhouse windows. First, cut the window glazing panels (1/4" clear polycarbonate is used here) using a circular saw and a straightedge guide. The glazing should equal the full height and width of the window. For convenience, this greenhouse was designed with all six windows exactly the same size.
Cut the rails and stiles for the window frame to length from 1 × 4 pine stock. Assemble the frame parts around the glazing panel, clamping them together temporarily. Use the glazing panel as an alignment reference: if the panel is square and the frame edges are flush with the glazing all around, your window is square.
Drill guide holes for the bolts that draw the window parts together. Use a bit that’s slightly larger than the diameter of the bolt shafts. This allows for slight expansion and contraction of the window parts as the temperature and humidity level change. Counterbore the bolt holes slightly.
Cut the arched inserts to fit at the top of the window frame opening. Install the inserts in the frame with glue and a couple of brads or pin nails. Install an insert on both the interior and the exterior sides of the window.
Attach door stop molding on the perimeter of each window opening, set so the window will be flush with the framed openings. Install fixed windows (if any) by centering the window unit in the opening side to side and driving a few 8d finish nails through pilot holes in the window and into the posts. Angle the pilot holes so the nail will not contact the glazing.
Install operable windows by centering the window unit in the opening, using shims to center it side-to-side and top-to-bottom. Hang the windows with exterior-rated pairs of butt hinges.
Install door pulls and eyehooks on the interior side of the window. Locate the pulls so they are centered and near the tops of the bottom window frame rails. Locate the eyehooks so there will be slight tension when the hook is in the screw eye—this will limit any rattling of the window.
Assemble the door frame. The center stiles should be attached to the frame rails with pocket screws or with deck screws driven toenail style. Clamp the parts together, sandwiching a piece of 1/4” polycarbonate between the frames.
Bolt the door together in the same manner as the window, drilling over-sized guide holes and counterboring slightly for the nuts. Install two or three bolts in the center stile area to keep the frame and glazing from separating.
Cut the door panel inserts with a jigsaw and sand them smooth. Insert them into the framed openings as shown in the Diagram shown here. Secure them on both sides of the glazing, using glue and brads or pin nails.
Hang the door. You may find it easier to paint it first. Door stop moldings should be installed so the door is flush with the outside greenhouse wall when closed. Add a latch and a handle. If you want to be able to lock the greenhouse, add a hasp and padlock.
Attach a garage door sweep (or comparable weatherstripping product) to cover the gaps between the greenhouse and the house. Flashing, such as drip cap, may be used to cover the gaps on the downsloping sides of the hip roof.
Make sure the foundation is clean and dry, then fill the gap between the concrete and the siding with clear silicone caulk.
Add trim elements to complete the roof. Parts of the roof trim system include: flashing over ridge (A); clear vent panel (B) attached with piano hinge (C) and automatic closer (D); seaming strip (E); metal drip cap for edges (F); 1/4 × 1 1/2" wood battens at rafter locations (G); vinyl cap molding at eave edges (H).
Finish the interior. You may add interior wallcoverings if you wish, but the exposed stud bays are good spots for adding shelving. For instructions on building this built-in potting bench, see here to here.
DIY Gabled Greenhouse
A greenhouse can be a decorative and functional building that adds beauty to your property. A greenhouse also can be a quick-and-easy, temporary structure that serves a purpose and then disappears. The wood-framed greenhouse seen here fits somewhere between these two types. The sturdy wood construction will hold up for many seasons. The plastic sheeting covering will last one to five seasons, depending on the materials you choose. It is easy to replace when it starts to degrade.
The 5-foot-high walls in this design provide ample space for installing and working on a conventional-height potting table. The walls also provide some space for plants to grow. For a door, this plan simply employs a sheet of weighted plastic that can be tied out of the way for entry and exit. If you plan to go in and out of the greenhouse frequently, you can purchase a prefabricated greenhouse door from a greenhouse materials supplier. To allow for ventilation in hot weather, we built a wood-frame vent cover that fits over one rafter bay and can be propped open easily.
You can use hand-driven nails or pneumatic framing nails to assemble the frame, if you wish, although deck screws make more sense for a small structure like this.
A wood-frame greenhouse with sheet-plastic cover is an inexpensive, semipermanent gardening structure that can be used as a potting area as well as a protective greenhouse.
TOOLS, MATERIALS & CUTTING LIST
(1) 20 × 50' roll 4- or 6-mil polyethylene sheeting
(12) 24"-long pieces of #3 rebar
(8) 8" timber screws
Compactable gravel (or drainage gravel)
Excavation tools
Level
Circular saw
Drill
Reciprocating saw
Maul
3" deck screws
Jigsaw
Wire brads
Brad nailer (optional)
Scissors
Utility knife
Tape measure
KEY |
PART |
NO. |
DIMENSION |
MATERIAL |
A |
Base ends |
2 |
3 1/2 × 3 1/2 × 96" |
4 × 4 landscape timber |
B |
Base sides |
2 |
3 1/2 × 3 1/2 × 113" |
4 × 4 landscape timber |
C |
Sole plates end |
2 |
1 1/2 × 3 1/2 × 89" |
2 × 4 pressure-treated |
D |
Sole plates side |
2 |
1 1/2 × 3 1/2 × 120" |
2 × 4 pressure-treated |
E |
Wall studs side |
12 |
1 1/2 × 3 1/2 × 57" |
2 × 4 |
F |
Ridge support |
1 |
1 1/2 × 3 1/2 × 91" |
2 × 4 |
G |
Back studs |
2 |
1 1/2 × 3 1/2 × 76" * |
2 × 4 |
H |
Door frame sides |
2 |
1 1/2 × 3 1/2 × 81" * |
2 × 4 |
I |
Cripple stud |
1 |
1 1/2 × 3 1/2 × 16" |
2 × 4 |
J |
Door header |
1 |
1 1/2 × 3 1/2 × 32" |
2 × 4 |
K |
Kneewall caps |
2 |
1 1/2 × 3 1/2 × 120" |
2 × 4 |
L |
Ridge pole |
1 |
1 1/2 × 3 1/2 × 120" |
2 × 4 |
M |
Rafters |
12 |
1 1/2 × 3 1/2 × 60" * |
2 × 4 |
*Approximate dimension; take actual length and angle measurements on structure before cutting.
How to Build a Gabled Greenhouse
Prepare the installation area so it is flat and well drained (See here); then cut the base timbers to length. Arrange the timbers so they are flat and level and create a rectangle with square corners. Drive a pair of 8" timber screws at each corner, using a drill/driver with a nut-driver bit.
Cut 12 pieces of #3 rebar to length at 24" (if necessary), using a reciprocating saw or hacksaw. Drill a 3/8"-diameter pilot hole through each timber, near both ends and in the middle. Confirm that the timber frame is square by measuring diagonally between opposing corners (the measurements must be equal). Drive a rebar spike through each hole, using a hand maul, until the bar is flush with the timber.
Cut the sole plates, caps, and studs for the two kneewalls. Mark the stud layouts onto the plates and caps, spacing the studs at 24" on center. Assemble each kneewall by driving 3" deck screws through the sole plates and caps and into the ends of the studs.
Install the kneewalls onto the timber base. Set each wall onto a side timber so the sole plate is flush with the ends and side edges of the timber frame. Fasten the sole plate to the timber with 3" deck screws.
Begin the endwalls by cutting and installing the end sole plates to fit between the side plates, using 3" deck screws. Cut the ridge support posts to length. Toenail one post at the center of each end sole plate. Check the posts with a level to make sure they’re plumb before fastening.
NOTE: The front post will be cut later to create the door opening.
Set the ridge pole on top of the support posts and check it for level. Install temporary cross braces between the outer wall studs and each support post, making sure the posts are plumb before fastening the braces. Double-check the posts and ridge for plumb and level, respectively.
Create a template rafter by cutting a 2 × 4 at about 66". Hold the board against the end of the ridge and the top outside corner of a wall cap. Trace along the face of the ridge and the cap to mark the cutting lines for the rafter. Cut along the lines, then test-fit the rafter and make any necessary adjustments for a good fit.
Mark and cut the remaining rafters, using the template to trace the cutting lines onto each piece of stock.
TIP: A jigsaw or handsaw is handy for making the bottom-end cuts without having to over-cut, as you would with a circular saw.
Install the rafters, using the deck screws driven at an angle into the kneewall caps and the ridge. The rafters should be aligned with the studs and perpendicular to the ridge.
Mark the two door frame studs by holding them plumb and tracing along the bottom edge of the rafter above. Position the studs on-the-flat, so the inside edge of each is 16" from the center of the support post (for a 32"-wide door, as shown). Install the studs with angled screws. Cut and install two studs on the rear endwall, spacing them evenly between the kneewalls and support post.
Complete the door frame: Mark the front support post 78" (or as desired) up from the sole plate. Make a square cut at the mark, using a circular saw or cordless trim saw (inset), then remove the bottom portion of the post. Cut the door header (from the post waste) to fit between the door studs. Fasten the header to the door studs and remaining post piece with screws.
Begin covering the greenhouse with the desired cover material (6-mil poly sheeting shown here), starting at the endwalls. Cut the sheeting roughly to size and secure it to the framing with wood tack strips fastened with wire brads. Secure the sheeting at the top first, the sides next, and the bottom last. Trim the excess material along the edges of the strips with a utility knife.
Attach sheeting to the edges of the sole plate on one side of the greenhouse, then roll the sheeting over the top and down the other side. Draw it taut, and cut it a little long with scissors. Secure the sheeting to the other sole plate (using tack strips), then attach it to the outside edges of the corner studs.
Create the door, using a piece of sheeting cut a little larger than the door opening (or purchase a door kit; see photo below). Secure the top of the door to the header with a tack strip. Weight the door’s bottom end with a 2 × 4 scrap cut to length.
Freestanding Kit Greenhouse
Building a greenhouse from a prefabricated kit offers many advantages. Kits are usually very easy to assemble because all parts are prefabricated and the lightweight materials are easy to handle. The quality of kit greenhouses varies widely, though, and buying from a reputable manufacturer will help ensure that you get many years of service from your greenhouse.
If you live in a snowy climate, you may need to either provide extra support within the greenhouse or be ready to remove snow whenever there is a significant snowfall because the lightweight aluminum frame members can easily bend under a heavy load. Before buying a kit, make sure to check on how snowfall may affect it.
Kit greenhouses are offered by many different manufacturers, and the exact assembly technique you use will depend on the specifics of your kit. Make sure you read the printed instructions carefully, as they may vary from this project.
The kit we’re demonstrating here is made from aluminum frame pieces and transparent polycarbonate panels and is designed to be installed over a subbase of gravel about 5 inches thick. Other kits may have different subbase requirements.
When you purchase your kit, make sure to uncrate it and examine all the parts before you begin. Make sure all the pieces are there and that there are no damaged panels or bent frame members.
A perfectly flat and level base is crucial to any kit greenhouse, so make sure to work carefully. Try to do the work on a dry day with no wind, as the panels and frame pieces can be hard to manage on a windy day. Never try to build a kit greenhouse by yourself. At least one helper is mandatory, and you’ll do even better with two or three.
Construction of a kit greenhouse consists of four basic steps: laying the base, assembling the frame, assembling the windows and doors, and attaching the panels.
Kit greenhouses come in a wide range of shapes, sizes, and quality. The best ones have tempered-glass glazing and are rather expensive. The one at right is glazed with corrugated polyethylene and is at the low end of the cost spectrum.
Organize and inspect the contents of your kit cartons to make sure all of the parts are present and in good condition. Most manuals will have a checklist. Staging the parts makes for a more efficient assembly. Just be sure not to leave any small parts loose, and do not store parts in high-traffic areas.
A cordless drill/driver with a nut-driver accessory will trim hours off of your assembly time compared with using only hand tools.
Rent outdoor power equipment if you need to do significant regrading to create a flat, level building base. Be sure to have your local utility company inspect for any buried utility lines first. (You may prefer to hire a landscaping company to do regrading work for you.)
How to Build a Freestanding Kit Greenhouse
Establish layout lines for the gravel subbase, using stakes or batterboards and mason’s string. The excavation area for the subbase should be at least 2" wider and longer than the outside dimensions of the greenhouse kit base. Make sure the layout is perfectly square (the lines are perpendicular to one another) by measuring diagonally between opposing corners: the layout is square when the measurements are equal.
Excavate the site to a depth of 5", using the layout strings as a guide. As you work, use a straight 2 × 4 and a 4' level to check the excavation to make sure it is level and flat. Tamp any loose soil with a plate compactor or hand tamp. Cover the excavation with commercial-grade landscape fabric (do not use plastic; the membrane must be water-permeable). Fill the area with 2 or 3" of compactible gravel, grade and level it, then tamp it thoroughly. Add more gravel, level, and tamp for a final subbase depth of 5".
Assemble the greenhouse base, using the provided corner and end connectors. Set the base onto the subbase and make sure the base is level. Measure the diagonals to check for square, as before. Add a top dressing of gravel or other fill material inside the base, up to about 1" below the base’s top lip. Smooth and level the gravel as before.
Attach the bottom wall plates to the base pieces so that the flanged edges face outside the greenhouse. In most systems, the floor plates will interlock with one another, end to end, with built-in brackets.
Fasten the four corner studs to the bottom wall plates, using hold-down connectors and bolts. In this system, each corner stud is secured with two connectors.
Install the ceiling plates: Assemble the pieces for each side ceiling plate. Attach each side plate against the inside of the two corner studs along each side of the greenhouse, making sure the gutter is positioned correctly. Attach the front ceiling plate to the outsides of the corner studs at the front of the building.
Attach the other side ceiling plate along the other side, flat against the inside of the corner studs. Then attach corner brackets to the rear studs, and construct the back top plate by attaching the rear braces to the corners and joining the braces together with stud connectors.
Fasten the left and right rear studs to the outside of the rear floor plate, making sure the top ends are sloping upward, toward the peak of the greenhouse. Attach the center rear studs to the rear floor plate, fastening them to the stud connectors used to join the rear braces.
Install the doorway studs at either side of the greenhouse door on the front end of the building. Install the side studs along both side walls of the greenhouse.
Add diagonal struts, as directed by the manufacturer. The struts help to stiffen and square up the walls. As you work, take diagonal measurements between opposing corners at the tops of the walls, to make sure the structure remains square.
Fasten the gable-end stud extensions to the front and back walls of the greenhouse. The top ends of the studs should angle upward, toward the peak of the greenhouse.
Assemble the roof frame on a flat area near the wall assembly. First assemble the crown-beam pieces; then attach the rafters to the crown, one by one. The end rafters, called the crown beams, have a different configuration, so make sure not to confuse them.
With at least one helper, lift the roof into place onto the wall frames. The gable end studs should meet the outside edges of the crown beams, and the ends of the crown beams rest on the outer edge of the corner bracket. Fasten in place with the provided nuts and bolts.
Attach the side braces and the roof-window support beams to the underside of the roof rafters, as specified by the manufacturer’s instructions.
Build the roof windows by first connecting the two side window frames to the top window frame. Slide the window panel into the frame; then secure it by attaching the bottom window frame. Slide the window into the slot at the top of the roof crown; then gradually lower it in place. Attach the window stop to the window support beam.
Assemble the doors, making sure the top slider/roller bar and the bottom slider bar are correctly positioned. Lift the door panels up into place onto the top and bottom wall plates.
Install the panels one by one, using panel clips. Begin with the large wall panels. Position each panel and secure it by snapping a clip into the frame, at the intervals specified by the manufacturer’s instructions.
Add the upper panels. At the gable ends, the upper panels will be supported by panel connectors that allow the top panel to be supported by the bottom panel. The lower panels should be installed already.
Install the roof panels and roof-window panels so that the top edges fit up under the edge of the crown or window support and the bottom edges align over the gutters.
Test the door and window operation, and make any necessary adjustments so they open and close smoothly.
PVC Hoophouse
The hoophouse is a popular garden structure for two main reasons: it is cheap to build and easy to build. In many agricultural areas you will see hoophouses snaking across vast fields of seedlings, protecting the delicate plants at their most vulnerable stages. Because they are portable and easy to disassemble, they can be removed when the plants are established and less vulnerable.
While hoophouses are not intended as inexpensive substitutes for real greenhouses, they do serve an important agricultural purpose. And building your own is a fun project that the whole family can enjoy.
The hoophouse shown here is essentially a Quonset-style frame of bent 3/4-inch PVC tubing draped with sheet plastic. Each semicircular frame is actually made from two 10-foot lengths of tubing that fit into a plastic fitting at the apex of the curve. PVC tubes tend to stay together simply by friction-fitting into the fittings, so you don’t normally need to solvent glue the connections (this is important to the easy-to-disassemble and store feature). If you experience problems with the frame connections separating, try cutting 4- to 6-inch-long pieces of 1/2-inch (outside diameter) PVC tubing and inserting them into the tubes and fittings like splines. This will stiffen the connections.
A hoophouse is a temporary agricultural structure designed to be low-cost and portable. Also called Quonset houses and tunnel houses, hoophouses provide shelter and shade (depending on the film you use) and protection from wind and the elements. They will boost heat during the day, but are less efficient than paneled greenhouses for extending the growing season.
PVC HOOPHOUSE
TOOLS & MATERIALS
Hand sledge
Plastic tubing cutter or hacksaw
Wood or rubber mallet
Circular saw
Stapler
Drill
Utility knife
Stakes and mason’s string
Eye and ear protection
Tape measure
Work gloves
(5) 1/2" × 10' CPVC pipes
(14) 3/4" × 10' PVC pipes
(3) 3/4" PVC cross fittings
(2) 3/4" PVC T-fittings
16 × 24' clear or translucent plastic sheeting
(4) 16' pressure-treated 2 × 4s
2 1/2" deck screws
(1) 1" × 6' PE tubing (black, flexible)
Sheet plastic is an inexpensive material for creating a greenhouse. Obviously, it is less durable than polycarbonate, fiberglass or glass panels. But UV-stabilized films at least 6-mil thick can be rated to withstand four years or more of exposure. Inexpensive polyethylene sheeting (the kind you find at hardware stores) will hold up for a year or two, but it becomes brittle when exposed to sunlight. Some greenhouse builders prefer to use clear plastic sheeting to maximize the sunlight penetration, but the cloudiness of translucent poly makes it effective for diffusing light and preventing overheating. For the highest quality film coverings, look for film rated for greenhouse and agricultural use.
Plastic tubing and fittings used to build this hoophouse include: light-duty 3/4" PVC tubing for the frame (do not use CPVC—it is too rigid and won’t bend properly); 1/2" CPVC supply tubing for the frame stakes (rigidity is good here); polyethylene (PE) tubing for the cover clips; T-fittings and cross fittings to join the frame members.
How to Build a PVC Hoophouse
Lay out the installation area, using stakes and mason’s string. Stake the four corners to create a rectangle that is 10' wide and 15' long. To make sure the layout is square (the strings are perpendicular), measure diagonally between opposing corner stakes: when the measurements are equal, the layout is square.
Cut a 30"-long stake from 1/2" CPVC pipe for each leg of each frame hoop. Plastic pipe is easy to cut with a plastic tubing cutter or a hacksaw. Mark the layout strings at 36" intervals, using tape or a marker. Drive a stake at each marked location, using a hand sledge or hammer. Keep the stakes plumb and drive them in 20" deep, so only 10" is above ground.
Join the two legs for each frame hoop with a fitting. Use a T-fitting for the end hoop frames and a cross fitting for the intermediate hoop frames. No priming or solvent gluing is necessary. (The friction-fit should be sufficient, but it helps if you tap on the end of the fitting with a mallet to seat it.)
Slip the open end of one hoop-frame leg over a corner stake so the pipe is flush against the ground. Then bend the pipes so you can fit the other leg end over the stake at the opposite corner. If you experience problems with the pipes pulling out of the top fitting, simply tape the joints temporarily until the structure frame is completed.
Continue adding hoop frames until you reach the other end of the structure. Wait until all the hoop frames are in place before you begin installing the ridge poles. Make sure the cross fittings on the intermediate hoop frames are aligned correctly to accept the ridge poles.
Add the ridge pole sections to tie together the hoop frames. The correct length for the ridge poles depends on the socket depth of the fitting you use, so you’ll have to measure the fittings and calculate length of the ridge pieces. If necessary, tap the end of each ridge piece with a wood or rubber mallet to seat it fully in the fitting socket.
Cut four 2 × 4s to length (15' as shown). Cut the cover material to length at 16' (or as needed so it is several inches longer than the house at both ends). Staple one edge of the cover to one of the 2 × 4s, keeping the material taut and flat as you work from one end to the other
Lay another 2 × 4 over the first so their ends and edges are flush and the cover material is sandwiched in between. Fasten the two boards together with 2 1/2" deck screws driven every 24" or so. Position the board assembly along the base of the hoops and pull the free end of the material over the tops of the hoops to the other side.
Pull the cover taut on the other side of the house, and repeat the process of stapling it to one board then sandwiching with the other.
Secure the cover at the ends with 6" lengths of 1" PE tubing. Cut the tubing pieces to length, then slit them lengthwise to create simple clips. Use at least six clips at each end of the house. Do not use clips on the intermediate hoops.
Shed-Style Greenhouse
This unique outbuilding is part greenhouse and part shed, making it perfect for a year-round garden space or backyard sunroom, or even an artist’s studio. The front facade is dominated by windows—four 29- × 72-inch windows on the roof, plus four 29- × 18-inch windows on the front wall. When appointed as a greenhouse, two long planting tables inside the shed let you water and tend to plants without flooding the floor. If gardening isn’t in your plans, you can omit the tables and cover the entire floor with plywood, or perhaps fill in between the floor timbers with pavers or stones.
Some other details that make this 10- × 12-foot shed stand out are the homemade Dutch door, with top and bottom halves that you can open together or independently, and its traditional saltbox shape. The roof covering shown here consists of standard asphalt shingles, but cedar shingles make for a nice upgrade.
Because sunlight plays a central role in this shed design, consider the location and orientation carefully. To avoid shadows from nearby structures, maintain a distance between the shed and the structure that’s at least 2 1/2 times the height of the obstruction. With all of that sunlight, the temperature inside the shed is another important consideration. You may want to install some roof vents to release hot air and water vapor.
Building the Shed-Style Greenhouse involves a few unconventional construction steps. First, the side walls are framed in two parts: You build the square portion of the endwalls first, then move onto the roof framing. After the rafters are up, you complete the “rake,” or angled, sections of the side walls. This makes it easy to measure for each wall stud, rather than having to calculate the lengths beforehand. Second, the shed’s 4 × 4 floor structure also serves as its foundation. The plywood floor decking goes on after the walls are installed, rather than before.
With slight modifications, many ordinary sheds can be redesigned as greenhouses. The addition of glass roof panels turns this shed design into an effective greenhouse.
CUTTING LIST
PART |
QUANTITY/SIZE |
MATERIAL |
Foundation/Floor |
||
Foundation base & interior drainage beds |
5 cu. yds. |
Compactible gravel |
Floor joists & blocking |
7 @ 10' |
4 × 4 pressure-treated landscape timbers |
4 × 4 blocking |
1 @ 10' 1 @ 8' |
4 × 4 pressure-treated landscape timbers |
Box sills (rim joists) |
2 @ 12' |
2 × 4 pressure-treated |
Nailing cleats & 2 × 4 blocking |
2 @ 8' |
2 × 4 pressure-treated |
Floor sheathing |
2 sheets @ 4 × 8' |
3/4" ext.-grade plywood |
Wall Framing |
||
Bottom plates |
2 @ 12', 2 @ 10' |
2 × 4 pressure-treated |
Top plates |
4 @ 12', 2 @ 10' |
2 × 4 |
Studs |
43 @ 8' |
2 × 4 |
Door header & jack studs |
3 @ 8' |
2 × 4 |
Rafter header |
2 @ 12' |
2 × 8 |
Roof Framing |
||
Rafters—A & C, & nailers |
10 @ 12' |
2 × 4 |
Rafters—B & lookouts |
10 @ 10' |
2 × 4 |
Ridge board |
1 @ 14' |
2 × 6 |
Exterior Finishes |
||
Rear fascia |
1 @ 14' |
1 × 6 cedar |
Rear soffit |
1 @ 14' |
1 × 8 cedar |
Gable fascia (rake board) & soffit |
4 @ 16' |
1 × 6 cedar |
Siding |
10 sheets @ 4 × 8' |
5/8" Texture 1-11 plywood siding |
Siding flashing |
10 linear ft. |
Metal Z-flashing |
Trim* |
4 @ 12' 1 @ 12' |
1 × 4 cedar 1 × 2 cedar |
Wall corner trim |
6 @ 8' |
1 × 4 cedar |
Roofing |
||
Sheathing |
5 sheets @ 4 × 8' |
1/2" exterior-grade plywood roof sheathing |
15# building paper |
1 roll |
|
Drip edge |
72 linear ft. |
Metal drip edge |
Shingles |
2 2/3 squares |
Asphalt shingles—250# per sq. min. |
Windows |
||
Glazing |
4 pieces @ 31 1/4 × 76 1/2" 4 pieces @ 31 1/4 × 20 3/4" |
1/4"-thick clear plastic glazing |
Window stops |
12 @ 10' |
2 × 4 |
Glazing tape |
60 linear ft. |
|
Clear exterior caulk |
5 tubes |
|
Door |
||
Trim & stops |
3 @ 8' |
1 × 2 cedar |
Surround |
4 @ 8' |
2 × 2 cedar |
Z-flashing |
3 linear ft. |
|
Plant Tables (Optional) |
||
Front table, top & trim |
6 @ 12' |
1 × 6 cedar or pressure-treated |
Front table, plates & legs |
4 @ 12' |
2 × 4 pressure-treated |
Rear table, top & trim |
6 @ 8' |
1 × 6 cedar or pressure-treated |
Rear table, plates & legs |
4 @ 8' |
2 × 4 pressure-treated |
Fasteners & Hardware |
||
16d galvanized common nails |
5 lbs. |
|
16d common nails |
16 lbs. |
|
10d common nails |
1 1/2 lbs. |
|
8d galvanized common nails |
2 lbs. |
|
8d galvanized box nails |
3 lbs. |
|
10d galvanized finish nails |
2 1/2 lbs. |
|
8d galvanized siding nails |
8 lbs. |
|
1" galvanized roofing nails |
7 lbs. |
|
8d galvanized casing nails |
3 lbs. |
|
6d galvanized casing nails |
2 lbs. |
|
Door hinges with screws |
4 @ 3 1/2" |
Corrosion-resistant hinges |
Door handle |
1 |
|
Sliding bolt latch |
1 |
|
Construction adhesive |
1 tube |
|
*Note: The 1 × 4 trim bevel at the bottom of the sloped windows can be steeper (45° or more) so the trim slopes away from the window if there is concern that the trim may capture water running down the glazing (see WINDOW DETAIL).
BUILDING SECTION
FLOOR FRAMING PLAN
LEFT SIDE FRAMING
RIGHT SIDE FRAMING
FRONT FRAMING
REAR FRAMING
FRONT ELEVATION
REAR ELEVATION
RIGHT SIDE ELEVATION
SOFFIT DETAIL
FRONT & SIDE DOOR CONSTRUCTION
FRONT & SIDE DOOR CONSTRUCTION (DOORJAMB, REAR, DOOR HEADER)
HEADER & WINDOW DETAIL
WINDOW SECTION
WINDOW DETAIL
TABLE & LOWER WINDOW DETAIL
RAFTER TEMPLATES
RAKE BOARD DETAIL
How to Build a Shed-Style Greenhouse
Build the foundation, following the basic steps used for a wooden skid foundation. First, prepare a bed of compacted gravel. Make sure the bed is flat and level. Cut seven 4 × 4" × 10' pressure-treated posts down to 115 3/4" to serve as floor joists. Position the joists as shown in the FLOOR FRAMING PLAN. Level each joist, and make sure all are level with one another and the ends are flush. Add rim joists and blocking: Cut two 12' 2 × 4s (142 3/4") for rim joists. Fasten the rim joists to the ends of the 4 × 4 joists (see the FLOOR FRAMING PLAN) with 16d galvanized common nails.
Cut ten 4 × 4 blocks to fit between the joists. Install six blocks 34 1/2" from the front rim joist, and install four blocks 31 1/2" from the rear. Toenail the blocks to the joists. All blocks, joists, and sills must be flush at the top.
To frame the rear wall, cut one top plate and one pressure- treated bottom plate (142 3/4"). Cut twelve studs (81"). Assemble the wall following the layout in the REAR FRAMING. Raise the wall and fasten it to the rear rim joist and the intermediate joists, using 16d galvanized common nails. Brace the wall in position with 2 × 4 braces staked to the ground.
For the front wall, cut two top plates and one treated bottom plate (142 3/4"). Cut ten studs (35 3/4") and eight cripple studs (13 1/4"). Cut four 2 × 4 window sills (311 1/16"). Assemble the wall following the layout in the FRONT FRAMING. Add the double top plate, but do not install the window stops at this time. Raise, attach, and brace the front wall.
Cut lumber for the right side wall: one top plate (54 7/8"), one treated bottom plate (111 3/4"), four studs (81"), and two header post studs (86 7/8"); and for the left side wall: top plate (54 7/8"), bottom plate (111 3/4"), three studs (81"), two jack studs (77 1/2"), two posts (86 7/8"), and a built-up 2 × 4 header (39 1/4"). Assemble and install the walls as shown in the RIGHT SIDE FRAMING and LEFT SIDE FRAMING. Add the doubled top plates along the rear and side walls. Install treated 2 × 4 nailing cleats to the joists and blocking as shown in the FLOOR FRAMING PLAN and BUILDING SECTION.
Trim two sheets of 3/4" plywood as needed and install them over the joists and blocking as shown in the FLOOR FRAMING PLAN, leaving open cavities along the front of the shed and a portion of the rear. Fasten the sheets with 8d galvanized common nails driven every 6" along the edges and 8" in the field. Fill the exposed foundation cavities with 4" of gravel and compact it thoroughly.
Construct the rafter header from two 2 × 8s cut to 142 3/4". Join the pieces with construction adhesive and pairs of 10d common nails driven every 24" on both sides. Set the header on top of the side wall posts, and toenail it to the posts with four 16d common nails at each end.
Cut one of each “A” and “B” pattern rafters using the RAFTER TEMPLATES. Test-fit the rafters. The B rafter should rest squarely on the rafter header, and its bottom end should sit flush with outside of the front wall. Adjust the rafter cuts as needed, then use the pattern rafters to mark and cut the remaining A and B rafters.
Cut the 2 × 6 ridge board (154 3/4"). Mark the rafter layout onto the ridge and front and rear wall plates following the FRONT FRAMING and REAR FRAMING. Install the A and B rafters and ridge. Make sure the B rafters are spaced accurately so the windows will fit properly into their frames; see the WINDOW SECTION.
Cut a pattern “C” rafter, test-fit, and adjust as needed. Cut the remaining seven C rafters and install them. Measure and cut four 2 × 4 nailers (311 1/16") to fit between the sets of B rafters (as shown). Position the nailers as shown in the HEADER & WINDOW DETAIL and toenail them to the rafters.
Complete the rake portions of each side wall. Mark the stud layouts onto the bottom plate, and onto the top plate of the square wall section; see the RIGHT and LEFT SIDE FRAMING. Use a plumb bob to transfer the layout to the rafters. Measure for each stud, cutting the top ends of the studs under the B rafters at 45° and those under the A rafters at 30°. Toenail the studs to the plates and rafters. Add horizontal 2 × 4 nailers as shown in the framing drawings.
Create the inner and outer window stops from 10'-long 2 × 4s. For stops at the sides and tops of the roof windows and all sides of the front wall windows, rip the inner stops to 2 1/4" wide and the outer stops to 1" wide; see the WINDOW SECTION and WINDOW DETAIL. For the bottom of each roof window, rip the inner stop to 1 1/2"; bevel the edge of the outer stop at 45°.
Install each window as follows. Attach inner stops as shown in the drawings, using galvanized finish nails. Paint or varnish the rafters and stops for moisture protection. Apply a heavy bead of caulk at each location shown on the drawings (HEADER & WINDOW DETAIL, WINDOW SECTION/DETAIL, TABLE & LOWER WINDOW DETAIL). Set the glazing in place, add another bead of caulk, and attach the outer stops. Cover the rafters and stop edges with 1 × 4 trim.
Cover the walls with T1-11 siding, starting with the rear wall. Trim the sheets as needed so they extend from the bottom edges of the rafters down to at least 1" below the tops of the foundation timbers. On the side walls, add Z-flashing above the first row and continue the siding up to the rafters.
Install 1 × 6 fascia over the ends of the A rafters. Keep all fascia 1/2" above the rafters so it will be flush with the roof sheathing. Using scrap rafter material, cut the 2 × 4 lookouts (5 1/4"). On each outer B rafter, install one lookout at the bottom end and four more spaced 24" on center going up. On the A rafters, add a lookout at both ends and two spaced evenly in between. Install the 1 × 6 rake boards (fascia) as shown in the RAKE BOARD DETAIL.
Rip 1 × 6 boards to 5 1/4" width (some may come milled to 5 1/4" already) for the gable soffits. Fasten the soffits to the lookouts with siding nails. Rip a 1 × 8 board for the soffit along the rear eave, beveling the edges at 30° to match the A rafter ends. Install the soffit.
Deck the roof with 1/2" plywood sheathing, starting at the bottom ends of the rafters. Install metal drip edge, building paper, and asphalt shingles. If desired, add one or more roof vents during the shingle installation. Be sure to overlap shingles onto the 1 × 4 trim board above the roof windows, as shown in the HEADER & WINDOW DETAIL.
Construct the planting tables from 2 × 4 lumber and 1 × 6 boards, as shown in the TABLE & LOWER WINDOW DETAIL and BUILDING SECTION. The bottom plates of the table legs should be flush with the outside edges of the foundation blocking.
Build each of the two door panels using T1-11 siding, 2 × 2 bracing, a 2 × 4 bottom rail, and 1 × 2 trim on the front side; see the DOOR CONSTRUCTION drawings. The panels are identical except for a 2 × 4 sill added to the top of the lower panel. Install 1 × 2 stops at the sides and top of the door opening. Hang the doors with four hinges, leaving even gaps all around. Install a bolt latch for locking the two panels together.
Complete the trim details with 1 × 4 vertical corner boards, 1 × 4 horizontal trim above the front wall windows, and ripped 1 × 4 trim and 1 × 2 trim at the bottom of the front wall windows (see the TABLE & LOWER WINDOW DETAIL). Paint the siding and trim, or coat with exterior wood finish.
Sun Porch Kit
A sun porch, a sunroom, a three-season porch, a greenhouse, a hothouse, an orangerie, a conservatory . . . these names are not precisely interchangeable, but all refer to a similar type of room. The common element all types share is that their walls and usually their roofs are made of clear panel glazing that allows light in and traps it, raising the ambient room temperature to more comfortable levels in cooler times of year. Some of these structures are designed for gardening-related activities; others are meant for enjoyment or entertainment. Some are freestanding, others are attached to a house.
If it is custom-built for you by a professional contractor, a sunroom can be quite expensive. But there is another option: a sunroom in a box. You can have a complete, do-it-yourself sunroom kit delivered to your home in cardboard boxes. A good deal of assembly is required, of course, but with a few basic tools and a helper, most people with basic DIY skills can complete the job in a weekend.
The key features of this sun porch (manufactured by SunPorch Structures Inc., see Resources) are its easy installation and its versatility. First, it’s designed to install right on top of an existing concrete patio slab or a wood deck, eliminating the extensive site-prep work required with a custom project. If you don’t have a patio or deck in place, you can build an inexpensive foundation with landscape timbers to support the sunroom structure, then create a floor inside using brick pavers, stone, wood decking tiles, or other suitable material. The sunroom manufacturer and your local building department can help you with the planning and construction details.
The sunroom’s versatility is apparent in both its design and use. Its modular construction allows you to specify the height, width, and length of the structure to fit your needs and your house. Other modifications can be made at the factory to accommodate special installation requirements, such as installing the room to fit against the roof eave of your house or even slightly above the eave. The standard room design includes two matching endwalls and a front wall. If your sunroom will fit into a corner where two house walls meet, simply order the room without one of the endwalls. The sizes of endwalls also can be adjusted to fit other house configurations.
Operable and removable windows make this sunroom versatile to use. In cooler months, all the windows can be closed against the cold to keep the sun’s heat inside. As the weather warms up, you can open either the top or bottom window sash to capture the breezes. And in the summer, you can take the windows out completely to convert the sunroom into a fully screened patio room.
Commercial-grade, lightweight glazing, and predrilled aluminum frame parts are the key components that make this sunroom kit lightweight and durable enough for shipping and also easy to assemble. Sunrooms can be perfectly acceptable spaces for evening activities, if you equip them with light fixtures (below).
Sun Porch Kit Accessories
Skylight shades give you control over light and heat coming through the roof panels. These 2-in-1 shades have a solid reflective panel that blocks most of the sun’s light and heat and a translucent panel that blocks only half of the sunlight to reduce glare and heat gain while letting light filter through.
Precisely fitted wall shades are convenient for reducing glare and heat gain right where you need it. They’re also great for adding privacy when and where you want it without blocking all of your sunroom views.
Optional roof vents allow hot air to escape and help to flush the interior of the sunroom with fresh air. Adjustable covers let you control the rate of airflow. The opening and closing mechanism is easy to operate from inside the sun porch.
Options for Attaching a Sun Porch to Your House
Attach the ledger directly to the wall if there is no eave overhang or if there is at least 6" of clear working space between the top of the ledger and the bottom of the eaves.
If the maximum height of the sun porch brings it up against or within 6" of the bottom of the eave overhang, extend the fascia on the eave downward and fill in with boards or siding between the cornice and the back post for the sun porch.
The ledger for the sun porch can be attached directly to the fascia board as long as the highest point of the sun-porch roof remains slightly lower than the roof covering. Be sure to attach the ledger so the lag screws hit into the ends of the rafter tails.
If the sun porch is slightly taller than the roof eaves, you can add a ledger that’s taller than the fascia, but it cannot extend more than a couple of inches higher. Fill in the open area beneath the roof covering created at the side using a full-width wood wedge and caulk. The roof covering must retain a slight slope with no swales.
Preparing the Installation Site
When attaching a sun porch directly to your exterior wall, install 2 × 6 or 2 × 8 edges and hang the roof support beams from it. Also install 2 × 4 vertical nailers beneath the ends of the edges for attaching the walls to the house. Ledgers also may be mounted to rafter ends in the eave area (see here).
Sun porch kits with nonglass panels can be mounted on practically any hard surface because they are light enough that they do not require a reinforced floor. You do need to make sure the floor is level, however (see here), and that the base channels you lay out create square corners.
The Benefits of Roof Ventilation
Without roof vents, hot air is trapped in the sunroom, making it uncomfortable for users and inhospitable to plants.
A single roof vent creates an escape route for hot air, allowing you to regulate the temperature and keep the room cooler during hot weather. Multiple roof vents increase the ventilation efficiency, but increase the chances for leaks.
Options for Anchoring a Sun Porch
On concrete patios, attach the base channel to the concrete surface with masonry anchors. There are many styles of anchors you can use. The hardware shown here is a wedge anchor that is driven into a hole drilled through the base channel and into the concrete. If your concrete slab is not level, you’ll need to insert shims underneath the base channel in low spots.
Building a new ground-level deck is a good way to create a stable floor for your sun porch if your concrete patio is in poor condition or if there is no other floor structure in the installation area. Attach pressure-treated 2 × 4 sleepers to the concrete surface to create a raised surface to set the deck on.
Set treated wood timbers onto a concrete footing for a sturdy wall base that you can attach to directly when installing the base channels. The footings should extend below your frost line to keep the structure from shifting, but you can use a less permanent floor system, such as sand-set pavers, if you wish.
TOOLS & MATERIALS
4' level
Drill and bits
Hex nut drivers (1/4", 3/8")
#2 square screw (Robertson) bit
Socket wrench set
Chalk line
Tape measure
Caulking gun
Rubber mallet
Pressure-treated lumber (2 × 4, 2 × 6)
Exterior house paint
Metal roof flashing
Step ladder
100% silicone caulk
Corrosion-resistant lag screws and washers (1/4" × 1 1/2", 1/4" × 2 1/2")
Additional fasteners for securing sunroom to house and supporting surface
SUN PORCH TERMS
Mounting surface: May be a level wood deck, concrete slab or patio.
Right and left endwalls: Reference point is with your back to the house looking outwards.
Kneewall (not shown): A site-built wall used to increase the height of the structure.
DOOR INFORMATION
Door (included with kit) may be mounted in any front or endwall bay.
Door opening is 33" wide and 72" high.
Door swings outward and can be hinged for left-hand or right-hand operation.
How to Build a Sun Porch Kit
Install pressure-treated 2 × 4 vertical support cleats and a 2 × 6 horizontal support ledger onto the house wall, following the manufacturer’s specifications (See here for options). On nonlap siding, mount the support pieces directly over the siding. For lap siding, cut away the siding and mount the ledger and support cleats over the wall sheathing and building paper. Paint the ledger and cleats before installation, and add roof flashing over the header, leaving it unfastened until the sunroom roof is completely assembled. Make sure the ledger is perfectly level and the vertical cleats are plumb.
Lay out the base channel pieces onto your surface in the installation area. Join the pieces using the provided splice brackets and screws.
Position the free ends of the base channel against the wall cleats. Use a 4' level to make sure the channel sections are level. If necessary, use tapered shims to level the channel. Then, check the base frame for square by measuring diagonally from corner to corner. Make adjustments as needed until the measurements are equal.
Fasten the base frame to the surface using a recommended fastener at each of the predrilled mounting holes. Apply a bead of silicone caulk where the channel meets the surface on both sides of the channel. Install the base channel vertical brackets to the base channels using the provided screws (inset photo). These brackets will join the vertical end-wall tubes and front-wall columns to the base channel frame.
To begin assembling the wall and roof structures, first join the endwall headers (the two outside rafters) and the rafters (the interior rafters) to the front-wall columns using the provided mounting brackets and screws. Also install the mounting brackets onto the free ends of the headers and rafters; these are used to mount the headers and rafters to the 2 × 6 support ledger (per step 1 shown here) on the house wall.
Complete the endwall assemblies by joining the vertical wall tubes to the endwall headers using the provided hardware. Finally, install the mullion brackets onto the sides of the rafters and endwall headers; these will join the horizontal mullions to the rafters and headers to tie the roof frame together (see Step 11).
With a helper, raise one of the endwall assemblies into position and set the vertical tubes over the base channel brackets. Fasten the tubes to the brackets with screws. Install the other endwall assembly the same way.
Anchor the endwall assemblies to the 2 × 4 support cleats and the 2 × 6 support ledger on the house wall. Use a level to position the vertical tubes perfectly plumb, and secure the tubes to the cleats using the recommended fasteners driven through the predrilled holes. Secure the endwall headers to the 2 × 6 support header using the recommended fasteners.
Snap a chalk line across the face of the 2 × 6 support ledger so the line is flush with the tops of the endwall headers. This line corresponds to the tops of the rafters and the bottom edge of the top mullion pieces.
Working from one endwall to the other, position the first rafter-front column assembly in place, and secure the column to the base channel using the provided screws. Then, install the horizontal mullions between the endwall header and the first rafter using the provided screws. Repeat this process to install the remaining rafter assemblies and mullions.
Install the top mullion pieces: Apply silicone caulk to the 2 × 6 support ledger to seal the vertical flange of the top mullions to the ledger. Also caulk where the horizontal flanges of the mullions will meet the endwall headers and rafters. Working from the right endwall to the left, secure the top mullions to the endwall headers and the rafters using the provided screws.
Anchor the rafters to the 2 × 6 support ledger using the recommended fasteners driven through the mounting brackets you installed on the rafter ends in Step 6.
Install the header caps over the tops of the endwall headers; these will help secure the roof glazing panels. First apply a bead of caulk down the center of each header, stopping it 3" from the end of the header. Set each cap into the wet caulk and secure it with the provided screws. Install the rafter caps following the same procedure.
Install the eave mullions over the exposed ends of the rafters and endwall headers. Apply caulk over the center of each frame part and around each predrilled hole. Set the mullions into the wet caulk and secure them with screws.
NOTE: Complete all additional caulking of the framing as recommended by the manufacturer.
Prepare the roofing panels for installation by taping the ends. Cover the top end of each panel with a strip of aluminum tape, and cover the bottom end with vented tape; both tapes are provided. Follow the manufacturers instructions to install any optional roof vents.
Apply adhesive foam gasket strips (provided) to the roof battens that will secure the glazing panels to the roof framing, following the manufacturer’s directions. Be careful not to pull or stretch the gaskets. Also apply gaskets to the roof framing, along the endwall headers, rafters, top mullions, and eave mullions, as directed.
Remove the protective film from the first roofing panel, making sure the UV-protected side of the panel is facing up. With a helper, place the panel on top of the endwall header and the adjacent rafter at one end of the roof. The panel should rest against the eave mullion along the front wall.
Secure the outside edge and ends of the panel with the appropriate battens, using the provided screws. To fasten battens to the eave mullion, first drill pilot holes into the mullion, using the predrilled batten holes as a guide. Carefully caulk the panel and battens at the prescribed locations.
Position the next roofing panel onto the rafters, and secure it with battens. The long, vertical batten covers both long edges of the first two panels.
TIP: You have to reach across a panel to fasten vertical battens. This is easiest when you have a tall ladder and use a magnetic nut driver on your drill, which allows you to drive the screws with one hand. Complete the flashing details along the 2 × 6 roof header as directed.
Install the remaining roofing panels, following the same procedure. Be sure to caulk the roofing carefully at all prescribed locations.
Begin the wall section installation by adding a triangular aluminum filler piece to the front section of each endwall. Install the fillers with the provided brackets and screws, then caulk along the top and ends of the fillers as directed.
Apply sealant tape along the perimeter of the first section on the front wall. Press the strips of tape firmly together to create a seal at each corner.
TIP: Storing the roll of tape in the refrigerator prior to installation makes it easier to work with.
Determine the door location (see TIP). Install the first screen/window frame. Set the panel onto the base channel, making sure the frame’s weep holes are at the bottom. Align the frame within the opening, and press inward firmly to seat it into the sealant tape. Secure the frame with the provided screws. Install the remaining frames using the same techniques.
Install the trapezoidal windows under the headers on the endwalls. Apply sealant tape as before, position the window, then secure it with the provided screws.
Complete the window installation by removing the bottom and top sash of each window frame. Peel off the protective film from the glazing, then reinstall each sash, following the manufacturer’s directions.
Begin the door installation by fastening the door threshold to the base channel, using the provided screws. Then, add the weatherstripping to the hinge bar and latch bar pieces and the header piece. Trim the excess weatherstripping.
Decide which side of the door will be hinged. Align the hinge bar (with door attached) to the markings on the vertical wall tube or front column, drill pilot holes, and mount the door to the column with screws.
Install the latch bar, leaving a 1/8" gap between the bar and the door edge. Install the header piece, also with a 1/8" gap. Complete the door assembly to add the handle, sweep, and closer, following the manufacturer’s instructions.
Apply sealant tape to the door frame, and install the two glazing panels as directed. Add the decorative cover on each side of the door, seating it with a rubber mallet. If the door is located on one of the endwalls, install the trapezoidal window above the door, using the same techniques described in Step 24.
Low-Maintenance Sunroom
The term “sunroom” can refer to many different types of rooms, from conservatory-style networks of metal frames and glazing that covers the roof as well as the walls to just about any room in your house that has banks of windows to introduce direct sunlight. The sunroom shown in this project (see Resources) is a three-season porch that encloses a second-story walk-out deck. The room is a modular kit that was custom-fabricated to the homeowner’s exact design and then assembled on site. Except for some custom framing work where the rooflines intersect, the installation was accomplished in a single day.
Built from rigid PVC panels that fit into aluminum frames, this sunroom measures 14 × 14 feet with a 10-foot gable peak. The sidewalls are 7 feet high. The underlying deck area is covered with plywood sheathing that will become a substrate for the finished floor—here, vinyl tiles. The glazing on the windows of the room is a clear vinyl fabric that can stretch to absorb impact and accommodate seasonal changes in framework dimensions.
The installers featured in this project are professional carpenters contracted by the sunroom seller. Custom sunrooms such as this can be ordered and installed by do-it-yourselfers as well. As a percentage of the total package price you won’t save a lot by doing the labor yourself, however.
Although they are not seen in the photos, a number of electrical receptacles were installed in the sunroom floor. The feeder cables run back to the house through conduit in the deck joist cavities, because the solid foam panels in the walls and ceilings do not readily accept cables.
To prepare for this new sunroom addition, an old deck was replaced with a new, beefier model. It features a sturdy staircase with enough room on the left side of the addition for an open-air grilling area that is accessed through a door in the sunroom. Instead of decking, the deck area in the sunroom installation area is covered with 3/4" tongue-in-groove plywood sheathing.
Low-Maintenance Sunroom Kit Parts
Aluminum tracks secure the prefabricated wall panels. Shown are sections of floor track (A), vertical wall track (B), and upper wall track (C).
Fasteners for this sunroom include self-tapping hex-head screws (1") with low-visibility white heads (A), insulation screws (7") with 2"-dia. fender washers (B), and galvanized self-tapping hex-head screws (2") with self-sealing EPDM rubber washers (C).
Wall panels for sunroom kits consist of rigid PVC frames with foam insulation in the core. The window sash telescopes downward in four tracks to provide maximum ventilation when open.
Clear vinyl glazing stretches under impact and will not shatter or crack. It is also light enough in weight that sunroom kits often can be installed without structural reinforcement that may be required for units with glass-glazed windows.
Roof panels come in varying thicknesses depending on the thickness of the rigid foam insulation board that is used (here, 4"). The narrow filler panel seen here features washable PVC beadboard on the interior side to create a ready-to-go ceiling once it is installed. The exterior side of the panel is 5/8" oriented strand board (OSB) to create a surface for installing building paper and asphalt shingles.
How to Install a Low-Maintenance Sunroom
Install the aluminum floor track channels at the perimeter of the installation area. Use a bead of weatherproof silicone sealant and self-tapping, 2" hex-head screws with EPDM rubber washers to secure the track. Square layout lines should be marked prior to installation. If your plywood substrate layer is treated with ACQ or copper azole wood treatment, protect the aluminum tracks from corrosion by installing an isolation layer of PVC flashing (sold in rolls).
Prepare the house walls for installation of the vertical wall tracks. Mark a cutting line on the siding at the track location and remove siding so you can fasten the tracks to the wall sheathing.
TIP: Use a cordless trim saw with a standard blade installed backward to cut vinyl siding.
Remove gutters and other obstructions from the installation area. The exact requirements for this step depend on the configuration of your roof and how you will be tying into the roofline or wall to make space for the sunroom roof.
Install the vertical wall track channels with silicone sealant and self-sealing screws. If the wall sheathing will not accept screws and is not backed by plywood sheathing, you will need to install sturdy wood or wood sheathing backers to secure the track.
Install the first wall panel. In many cases, the first panel will be a narrow filler strip that is simply a solid wall panel and does not contain windows. Install the panel by driving 1" self-tapping screws through the floor track flanges and into the bottom frame of the panel. Make sure the panel is plumb and firmly seated against the track.
Add the next panel according to the installation sequence diagram that comes with your kit. Make sure the panel is plumb and then tack it into position by driving self-tapping screws through the floor flange. The panels lock together at the edges, which will hold them temporarily until the upper wall track can be installed. If you are working in windy conditions, you may need to brace the panels.
Install a corner post at the first corner. The flange on the side of the L-shaped post (inset photo) should capture the end of the first wall's last wall panel. The second wall's first wall panel will fit into the other leg of the L.
Fit the upper wall track over the entire first wall after cutting it to length. The end of the track that joins with the track on the next wall should be mitered to make a neat joint. If the adjoining wall is gabled, this will mean making a relatively tricky compound miter cut. Refer to your plan for the exact angle and don’t be shy about asking for help.
Continue installing panels on the second wall. If it is a gabled wall, install panels up to the midpoint; then cut the three-part, ridge pole support post to fit, and install it by driving screws through the post and into the wall panel. Make sure the saddle formed at the top of the post is sized to accept the ridge pole.
Install the remaining wall panels, creating corners and adding upper wall tracks as you go. Frequently check for plumb and level, and make sure all panels are seated firmly in the tracks.
Mark the upper wall tracks at the gable for cutting by transferring the edges of the ridge pole saddle onto the ends of tracks. Cut them to length and the correct angle with a power miter saw and metal cutting blade. Or, you can use an old combination blade that you don’t mind making dull.
Set the ridge pole into the saddle in the ridge pole post, and adjust it until the overhang is correct. Check the length: if the pole does not end at the correct point on the other end, recut it or adjust your overhang amount. Secure the end by driving screws through the ridge pole post and into the ridge pole.
Secure the house-end of the ridge pole. Begin by installing a temporary post near the house wall that is the same height as the bottom of the saddle opening in the ridge pole post. Make sure the ridge pole is level and then measure for attaching it to the house. The exact method you use depends on the house structure. Here, the exterior wall that will support the ridge is set back 18" from a pair of bay windows that are covered by the same roof. This means that the cap plate for the bearing wall that will support the ridge pole is lower than the bottom of the pole. The distance is measured (left photo) and a 2 × 6 half-lap post anchor is constructed. The anchor is nailed to the cap plate on the wall and then the ridge pole is attached to the anchor with deck screws (below photo).
Begin installing roof panels. The full-width panels seen here are 4' wide, yet they are strong enough to meet minimum dead load (“snow”) requirements even in cold climates. The panels are attached with long insulation screws that are fitted with fender washers and driven into the ridge pole and upper wall track.
Install I-beams on the roof next to the first roof panel. The track on one side of the I-beam should capture the leading edge of the first roof panel. Attach the I-beam to the roof panel with self-tapping screws driven through the I-beam flange and down into the OSB panel surface.
Add the next roof panel to the roof, sliding it into the open side of the I-beam. Square the panel with the roof, and then drive insulation screws down through the panel and into the ridge pole and the upper wall track. Add the next I-beam and fasten it with self-tapping screws.
Continue installing panels and I-beams until the roof is complete. Complete one full side before beginning the other.
Install fascia and gutters. The materials seen here are designed specifically to work with the roof panel system of this kit. The fascia snaps over the ends of the roof panels and is secured with screws. The gutters fit into tracks on the fascia and are secured with screws.
Install the prehung doors by fastening the door nailing flanges to the frames that create the door opening. Make sure the door is level and plumb before driving fasteners. Attach the door handle and latch.
Make finishing touches, such as trimming off excess insect screening and painting or cladding the ridge pole. If your sunroom does not have a finished ceiling, add one (tongue-and-groove cedar carsiding is a good choice). Install floorcoverings.