Building a Patio Roof
Updated: Sep 27, 2022
To make the most of a poolside patio area, the Laney family of Birmingham, Alabama, decided to add a patio roof to a balcony overhang. The new extension provides shelter from the rain and shade from the sun, covering a concrete patio that now includes cushioned seating, an outdoor television, a ceiling fan and a grilling station. The roof was built to blend seamlessly with the home’s construction and make a perfect place for watching a game poolside while burgers are cooking.
The builders on this project are the father-and-son remodeling team of Randy and Caleb Stephenson, who began with a strong foundation using pressure-treated posts on galvanized post bases. These days, building codes require “ground contact-rated” treated lumber for all outdoor posts as well as any key structural components that tie into the house or are located near the ground.
The roof was attached at one end to the balcony rim joist and supported on the other end by three 4x4 posts. Each post is lifted off the foundation by a galvanized post base secured in place with a concrete anchor. The separation protects the wood against rot by preventing standing water from wicking into the end grain of the lumber. Fastening the metal base into the sides of the post also increases uplift loads for wind resistance. Furthermore, this ABA post base from Simpson Strong-Tie is adjustable by including a slot around the anchor bolt that makes precise post placement easier.
Note that if you’re building in an area without an existing concrete foundation, HIR recommends you provide concrete piers beneath the posts to avoid direct ground contact with the wood.
At the house end, the roof’s ceiling joists are supported from below by a 2x4 ledger as well as by fasteners driven into the house framing. During construction, the ledger board was screwed in place for assembly (then later anchored with lag screws). The ledger board is installed over the painted fascia board of the house’s balcony, but directly behind the fascia is solid house framing.
Whenever attaching a structure to a house, first make sure solid 2x framing is located behind the trim or siding you’re fastening into. Trim boards are typically only 3/4-in. thick and don’t provide adequate support for the connection. For the ledger, joists and rafters, fasten with exterior-grade screws long enough to penetrate at least 1-1/2 in. into solid 2x framing.
Check for Height, Level and Squareness
Establishing a square and level layout is absolutely critical. Once you have the ledger attached and the posts temporarily braced in place, position the two band joists that frame the roof, extending from each end of the ledger to the support posts. These side joists should be attached over the posts completely square, level and at the same elevation as each other.
Anyone building at home should be prepared for some unexpected real-world issues, such as the uneven patio foundation Randy and Caleb were building on. When leveling the side joists, the patio slope meant one post was too high and had to be trimmed to length. The second post was slightly too short, and Caleb added a wood block to the top to make up the difference.
At the opposite end from the house, the three posts support the roof’s header, which is usually made of two vertically installed 2x boards that run parallel to the ledger to carry the joists and rafters. Whether you’ll need a 2x6, 2x8 or larger will be determined by the span of the header as allowed by your local building codes.
For shorter spans, you can attach the header boards on each side of 4x4 posts using carriage bolts and washers (fortified with epoxy to withstand weather exposure). For longer spans, you might consider using 6x6 posts notched on each side to accept the header boards, so the weight is transferred directly to the ground and not reliant solely on the shear strength of the bolts.
You’ll notice this roof incorporates an unusual approach to header construction. On this project, the Laney family wanted to preserve as much view of their pool and expansive backyard while sitting beneath the roof as possible, but the roof header threatened to obstruct that view. So, how do you “shrink” a porch roof header without compromising its strength?
Randy and Caleb came up with a three-fold solution: First, they built the roof with the shallowest pitch allowed by code. Second, they installed a 2x6 oriented flat rather than vertically, which shrunk the header height by several inches while still providing a nailing surface. A flat 2x has very little load-bearing capacity, though, so they incorporated 3/8-in. angle iron into the construction of the header to ensure it would not bow beneath the framing. Similar to a lintel that supports brickwork, this approach maintained the structural integrity of the header, but before attempting the same at your home, consult your local building inspector to see if it’s permitted in your area.
Joists and Rafters
Before installing joists and rafters check the boards and mark the crown, which refers to the direction of the arc in a bowed board. The crown (arc) should be oriented at the top when the boards are installed vertically to avoid sagging in the roof.
With the band joists and header established, the interior 2x4 joists were installed level on 16-inch centers, driven from each side and from the top into the house framing with 3-1/2-in. screws and supported by the ledger board. In some municipalities, local codes might require metal connectors to install the joists.
On the opposite end, the joists are screwed to the header, which supports them from beneath. The joist ends extend several inches past the header where they’ll tie into the rafter tails and ultimately be enclosed to provide a drip edge to the roof, so water will shed away from the structure and the patio.
Aligned with each joist, the 2x4 rafters were then toe-screwed into the house framing to give the roof its pitch. To help manage the pitch, Randy used a loose 2x4 oriented perpendicular across the joists on which he propped the rafters to help approximate their angle. He then used a 6-foot level to carefully check rafter height before fastening them in place.
Between each rafter and joist, Randy installed 2x blocking flush between the framing members to solidify construction and prevent any lateral movement.
Once the framing is complete, consider any additional rough-in work you might need, such as extra blocking to support a ceiling fan, as well as any electrical or other utilities that should be incorporated.
With the rafters complete, the Laney pool patio got its new roof. Caleb and Randy fastened plywood sheathing over the joists, Randy cap-nailed the underlayment in place, and the roof was covered in the same architectural shingles as they rest of the house to give it a perfect match. Be sure to install appropriate flashing where the patio roof meets the house, and if you’re not sure how to do that, call a pro.
With the shingles buttoned up, a similar roof might be ready for a coat of exterior stain/sealer to preserve the look of the exposed wood. This project, however, got the full paint-and-trim treatment to blend with the home, including a finished ceiling, enclosed header soffit, and decorative column wraps for the support posts.
Editor's Note: Randy Stephenson is a professional remodeling contractor in central Alabama, who can be reached by email at handyrandyco [a] yahoo.com.