How to Build a Porch Roof Step-by-Step

Building a porch roof requires installing foundational supports, and any project considered a “permanent improvement” like this will require permits. Head to your local building department to pull the proper permits for your porch roof to keep your project legal.

Installing a porch roof is also a major undertaking that requires lots of planning to avoid wasted materials and unnecessary trips to the home improvement store. Get all of your tools and materials together, and double-check that you have everything you need before you begin.

The ledger board is the horizontal piece of lumber that attaches to your home’s framing and supports the porch roof. You can start the installation by using your oscillating tool to cut out a piece of siding to reveal the wood behind it. Measure carefully to avoid cutting out too large of a hole.

Use 2-by-8 material for the ledger board, and attach it to your home’s exterior wall framing using 5-inch lag screws and washers. Finish the ledger board by installing deck flashing around it. Tuck the flashing behind the siding on all four sides of the ledger board for adequate protection.

Measure how far out you want your deck roof to extend and mark spots for the outer supports. Use your post hole digger to dig the holes. Check local regulations for how deep foundational supports need to be, as it varies based on the frost line and local building ordinances. Dig at least that far down.

Set the concrete building form tubes into the holes, and put down a 4-inch layer of gravel or paver base at the bottom. Mix and pour your concrete, and set the post bases into place. Double-check that the post bases are level and square to the exterior wall of your home.

Once the concrete dries, use your circular saw to cut the posts to the proper height. You’ll need to determine what roof pitch you want to get the right roof measurements.

Connect the two posts using a header beam made of 2-by-10 material and plywood. To make the header, cut two 2-by-10s to the proper length, sandwich a piece of plywood between them, and use a framing nailer to nail them together.

Next, you can attach the rafters. If you’re using rafter hangers on both sides, you can just cut the proper angle on the ends of the rafters and attach them to both the ledger board and the header. If not, you’ll need to notch the rafters on the ends nearer to the header to get them to sit properly. Use your circular saw to create the notches.

With the rafters in place, you can install the plywood or OSB roof decking. Be sure to review ladder safety tips before you begin. Use your table saw or circular saw to cut the sheets to size, and use your framing nailer to attach them. Always line up the edges of the plywood or OSB so that they rest on a rafter.

Install drip edge flashing along the length of the header and the two side rafters. Use roofing nails to secure the flashing in place. You can use tin snips to cut the drip edge flashing to length. Leave an additional inch of flashing so that you can cut at the corner and fold over the side and top pieces for a cleaner look.

Lay down your roof underlayment and attach it to the decking using the method recommended by the manufacturer. For roofing felt, you’ll usually use plastic cap nails. Ice and water shield has a pre-applied adhesive that just sticks to the underlayment. Be sure to extend the edges of the underlayment over the top of the drip edge flashing on all sides of the roof.

Finally, you can install the finished roofing material. Follow the manufacturer’s directions with respect to sealants, nail patterns, screw patterns, and shingle or panel overlap. The overhang for metal roofs and asphalt roofs on all edges of the roofing system should be between 1 and 3 inches unless you’re using gable end flashing to seal the sides.