Our porch is built over a hefty foundation of 6x6 preservative-treated pine timbers sunk in a crushed-rock base. Upright timber posts at each corner are notched and lag-bolted to the buried timbers. Each post is also lag-screwed to 2x6 treated joists. The joists hold the posts firmly in place and provide a decay-resistant framework to elevate the cedar decking above ground level. The spectacular open rafter roof is supported by cedar headers bolted to the posts and by stationary doors fastened to the corners. The curved corner brackets not only provide elegant detailing to each corner, but act as reinforced structural bracing (whatever you do, don't eliminate them).
Making the finely detailed doors is simplified by building a jig to hold the door parts square for accurate and foolproof assembly. The same jig also holds the door securely for stretching the screen, stapling it to the frame and then applying the decorative door moldings.
A project like this requires a fair amount of carpentry experience. If you've built a wooden yard shed, a complex deck or an intricate fence, you'll have the confidence to tackle this project. It'll also take a huge chunk of time, so plan to take a couple of weeks off work along with a few dedicated weekends (now is the time to call in all those favors from friends you've helped over the years).
You'll need basic carpentry tools for this job, with additional help from a table saw and router. You'll need a couple of stepladders for this project as well; we recommend a 6-ft. and a 12-ft. You may also want to rent a section of 6-ft. scaffolding to help with the roofing. Figure on spending about $4,000 to $5,000 for materials (see Cutting List in Additional Information, below) and get as much delivered to your home as possible.
Figure A: Overall Details
The total size of the screen house at the roof is 18 ft. by 15 1/2-ft. A printable, PDF version of this plan is available in Additional Information (below). Note that building codes in some regions require additional seismic and high-wind anchors. Ask your building inspector about local requirements.
This is not a small-scale project. At its longest points (the roof overhang) it measures just over 18 ft. long and 15-1/2 ft. wide. Keep these numbers in mind as you look for a place to nestle your structure. We shoehorned our screen house into the back yard of an average-size city lot and crowding the existing fence and surrounding trees. This nestling effect made it look as if the screen house grew into its surroundings.
Before you do any digging, call local utilities (gas, electrical, phone, cable) to locate any buried lines. Also make some plans to get rid of the extra dirt and sod you'll dig up. We ended up with about 1-1/2 cu. yds. to haul away.
Install the joists at each end first, then string a line between them. Align the ends of the other joists 3/4 in. from the string (use a spacer block on each end joist as shown). Then tack them in place, mark them and join them with blocks. The joists that butt against the posts must be lag-screwed to the sides of the posts to keep them from racking out of alignment.
Once you've staked out your perimeter on well-drained level ground (see Fig. C for the foundation dimensions), you'll need to dig trenches for the 6x6 treated beams (A). (Be sure they're .60 treated, rated for underground protection. Special-order them if necessary.) Follow the foundation plan in Fig. C for the correct placement. Dig each trench about 10 in. deep and 12 in. wide. Fill each trench with about 5 in. of crushed rock (we used crushed limestone because it packs well).
Now cut the beams to length and lay them in the trench (Photo 1). Level them with each other and make sure the diagonal measurements from the ends of the two outer beams are equal. This ensures that the foundation will have square corners. The beams should sit proud of the surrounding grade about an inch so the joists that lie over them can clear the soil. Once the beams are in place, pour crushed rock around them to lock them into position.
The next phase involves setting the posts (B) onto the beams. First, cut them to length and notch the bottom as shown in Photo 2. Measure in from the ends of the outer beams (A) as shown in Fig. C. Get a helper to hold the notched end of the post perfectly vertical (plumb) on the beam and aligned with the mark. Drill two 3/8-in. pilot holes through the post and into the beam. Now insert your lag screws (1/2 x 5 in.) and washers and tighten them (Photo 2). Repeat this for each post. TIP: If you're working alone, you can tack each post into position with nails and 2x4 braces.
Now you can lay in the joists as shown in Photo 3 and Fig. C. The joists that connect to the posts must be cut and blocked as shown in Fig. C. You can cut and block each pair of remaining joists, or you can overlap 10-ft. joists on the center beam. Just be sure the joists that butt against the posts are screwed to the posts with 1/2 x 3-1/2 in. lag screws, and all the joists are toenailed with three 16d galvanized nails where they overlap each foundation beam. To finish off the foundation, nail the five-quarter (5/4) decking (D) to the joists with 10d galvanized casing nails.
The upper headers (E1, E2, E3 and E4) fastened from post to post (Fig. D) are the main support for the roof. The stationary doors that fit later under the lower headers (M1 and M2) help support the roof as well.
When you install the inner headers (E1 and E2), be sure your posts are plumb and that the distance from post to post is identical at the top and bottom of the posts. Lag-screw (1/2 x 3-1/2 in.) the inner headers to the posts as shown in Photo 5, then nail the outer headers over the inner headers with a pair of 10d galvanized nails every 16 in.
Think of these supports as a structural skeleton to hold the roof skin in place. Our roof has three basic types of rafters: common, hip and jack. Pick your lumber for the rafters carefully because they'll be visible when the project is finished.
The common rafters (Photo 6) are all the same length and have the same miter cut at the top and the same “bird's-mouth” or notch cut near the bottom. Cut them to the dimensions in Fig. E and nail them to the ridge board (F). Support the ridge board temporarily with a 12-ft. 2x6 toenailed to the decking and to the ridge itself. The top of the ridge should be roughly 123 in. up from the decking (you may need to raise or lower it slightly for a tight fit for the miter cuts on the rafters). Once you like the fit, fasten all the common rafters to the ridge board with 16d galvanized nails. Nail the rafters through the ridge from the back to hide the nailheads.
The four hip rafters (Photo 8) rest over each corner and meet the ends of the ridge board. You'll notice that the upper miter is a compound cut. This miter angle differs from that of the common rafters (Fig. E), and you'll notice it has a 45-degree bevel cut on each side along with the miter cut. This allows the hip rafters to fit snugly between the common rafters. The bird's-mouth notch is also unusual because it sits at an angle to the common rafters. You can leave a bit of extra length at the overhang of each hip rafter and trim it to final length once the other rafters are in place.
The jack rafters (Photo 8 and Fig. E) rest on the header just like the common rafters and have the same degree measurement at the top. However, the edge of the jack rafter has a 45-degree bevel (a cheek cut) so it fits tight against the hip rafter. Toenail each of these cheek cuts to the side of the hip with three 8d galvanized nails. Note that the cheek cuts (Fig. E) on each side of the hip rafter are mirror images of each other.
When you're finished installing the rafters, nail the subfascia (H1, H2) to the tails of the rafters and install the 2x6 lower headers (M1, M2) directly beneath the upper headers. Also nail (8d galvanized casing) the 5/4 header trim (M3, M4) to finish off the transition between the upper headers and the lower header.
TIP: Before you set the roof boards over the rafters, nail temporary 2x4 braces on two sides of the structure, from the middle of the header diagonally to the bottom of the post. This will minimize any racking during the building process.
Nail the 1x6 cedar roof boards (J) to the tops of the rafters after installing the subfascia (H1 and H2) over the exposed ends of the rafter tails. Leave a 1/8-in. space between the boards and alternate end joints so they don't all fall on the same rafter. We used a combination of 12-ft. and 8-ft. long boards. Finish opposite sides first, then trim the board ends to length all at once (set your circular saw at a 15-degree bevel).
Much of the beauty of the interior comes from the 1x6 cedar boards visible between the rafters. These boards alone, however, aren't enough to give stability to the structure, so they're backed with 5/8-in. CDX plywood. The plywood also adds enough thickness to keep the shingle nails from poking through the underside of the roof.
First, nail the 1x6 roof boards to the rafters (Photo 9) with 8d nails. Start at the bottom flush with the ends of the rafters and work your way to the top, leaving a 1/8-in. clearance between the boards. Overlay the plywood onto the 1x6 and nail it through the plywood and roof boards into the rafters with 10d nails.
Once the plywood layer is complete, nail the finished fascia (L1, L2) over the subfascia and align it with the bottom edge of the plywood. Next, roll on the 30-lb. roofing felt and overlap each layer by 3 in. Then nail the No. 2 cedar shingles to the roof deck (Photo 11) with 4d galvanized nails (follow the positioning instructions that come with each bundle). The first course of shingles must be double thickness and overhang the fascia (L1, L2) by 1 in.
You'll need to trim the cedar shingles to conform to the angle above the hip as you lay them. Once you've finished shingling, cover the gaps over the hip by ripping 4-in. wide pieces of shingle to create a cap over the hips and ridge.
Assemble each door using a jig to ensure each frame is square. Apply construction adhesive to the lap joints on each corner, then screw the parts of each lap joint together with five 1-1/4 in. decking screws. Keep the screws at least 1 in. from the edges of the frame because you'll need to trim the door to size later.
Making the doors is the most time-consuming part of the project, so we broke it down into manageable tasks. Since you can build them in the garage on a work table, it's the perfect job for rainy days.
First cut the door stiles (side pieces) and the rails (upper and lower horizontal pieces) to length. Then set up a simple jig (Photo 12) to use with your router to make the half-lap joints on the ends of all the stile and rails. Use a 3/4-in. straight bit. If you have a table saw, you could make the half laps with a dado blade.
The next step is to set up a 3/4-in. thick, 4 x 8-ft. plywood work surface over a pair of sawhorses. Use scrap wood to make blocks (Photo 13) to hold the door parts square.
Before you apply screen to the door frames, flip them over so the screws are on the back and then staple the screen as shown in Photo 14. Once the screen is applied to the doors, you can cut the moldings (see Fig. G) from 2x6 cedar (use a table saw) and nail them to the door frame with small screen molding nails.
Before you install the doors, nail the cleats to the deck (Photo 16) and the upper doorstop to the inside edge of the lower header. It's best to use a string line to mark the deck to get the floor cleats positioned in a straight line. To align the doors properly in the opening, find the center of each side and measure each door width (mark it off on the deck) back to the corners.
You may have to trim each door's height slightly to fit the opening. The stationary doors should fit snugly, and the operable doors need 3/16-in. clearance on the bottom and 1/8-in. on the top. Screw the corner doors to the post (the door edge should cover roughly half the post), the upper doorstop and the lower floor cleat. The longer side has an additional door, which should be positioned tight to the corner door and nailed to the floor cleat and the upper doorstop.
The operable doors (the double doors on the front and back, and the single on the long side) must be shimmed on the bottom and top (Photo 18). This will hold them in place while you screw the self-closing hinges to the adjacent stationary door frame and the swinging door. Remove the shims and make sure the operable doors swing freely. To finish the door system, you'll need to install the vertical stop (P5, P6, P7) as shown in Fig. A to the back of the doors. This trim runs from the floor cleats to the upper doorstop, covers the gaps between the doors and finishes off the interior.
Finish each exposed post with a cedar 2x4 and a 2x6 (T1 and T2; see Fig. H) that are ripped to width and then cut to length. Be sure the front of the screen house has the wider piece to overlap the longer side post trim.
Cut the bracket supports and the curved corner brackets (U1, U2) as shown in Fig. H. Notice that the top of the bracket support is notched to fit over the header trim. Screw the bracket supports (predrill all these holes) to the corner trim with 3-1/2 in. galvanized screws (use three screws for each bracket). Next, screw the curved corner bracket to each bracket support (two screws on each side) and to the upper jack rafter (four 3-in. screws here).
Now you're ready to clean up the work site and enjoy the rest of the summer in your beautiful outdoor space.
- Figure G: Door Assembly
- Figure H: Corner Details
- Cutting List
- Hardware & Miscellaneous
- Figure A: Overall Details
- Figure B: Completed View
- Figure C: Foundation Plan
- Figure D: Roof Framing
- Figure E: Rafter Details
- Figure F: Eave Details