How to Build a Porch Roof
Porches are a great complement to any home. These supplementary living spaces let you relax outdoors while still enjoying the comforts of dry, elevated flooring and easy access to the house. But uncovered porches are less useful than covered porches. Rain and sun limit your time outside, plus porches that receive the brunt of the elements will deteriorate much faster. When you build a porch roof, you extend the porch season and you protect the porch and the side of your house.
Basics of Building a Porch Roof
Porch roof construction can be as simple as building a shingled lean-to that projects off of the side of the house, supported by vertical columns. It's not a complicated task, but heavy building materials are involved and it always helps to have an assistant on the job.
Porch Roof Angle
It is usually best to angle, or pitch, the porch roof. Flat porch roofs are more difficult to waterproof and have a greater possibility of leaking. Porch roofs that pitch downward promote water drainage. For visual appeal, the porch roof's angle ideally should match the angle of the house's roofing.
The minimum roof pitch will be determined by the type of roofing used. The standard 3 tab or architectural laminate shingles require a minimum of 2 to 12 slope. If the roof slope is less than that, an alternate type of roofing will be required.
Attaching the Porch Roof to the House
One of the most critical components of the porch roof is its ledger board. The ledger board takes advantage of the house's strength to support the highest edge of the porch roof. The ledger board supports half of the porch roof's weight. Metal drip flashing installed between the porch roof and the house siding prevents water leakage.
What Is a Ledger Board?
A ledger board is any type of dimensional lumber installed horizontally on a structure to provide partial support for another, smaller structure, such as a porch roof, patio roof, or deck.
Header Beam and Posts
If the ledger board supports half of the porch roof, the header beam and posts support the other half. Vertical six-by-six support posts spaced every eight feet are securely embedded in concrete footers. The posts hold up a header beam. The header beam runs parallel to but lower than the ledger board.
The finishing touch of the porch roof is its shingles. Whenever possible, the porch shingles should match the house's roofing shingles.
Codes and Regulations
In most communities, any accessory structure that attaches to the residence must be permitted. Porch roof plans will need to be reviewed and approved by the local permitting office. In some cases, you may be required to have an architect or engineer develop the plans.
What You'll Need
Equipment / Tools
- Cordless drill
- Ratchet wrench set
- Circular saw
- Post hole digger
- Speed Square
- 7 two-by-sixes
- 1 two-by-ten
- 2 six-by-sixes, 10-foot
- 15 lag screws with washers, 5-inch
- 6 rafter hangers for two-by-sixes
- 4 bags of quick-set concrete
- 2 bags of gravel
- Plywood house sheathing, 1/2-inch
- Drip flashing, 8-foot
- Shingles, 1 square
Attach the Ledger Board
Strip siding and sheathing from the house to expose a section of band joist or structural framing that is 8 feet long by 5-1/2 inches high. After drilling pilot holes, use the ratchet wrench to install the two-by-six board to the house with the lag screws and washers.
Install the Rafter Hangers
Screw the rafter hangers to the ledger board every 16 inches. One rafter hanger should be at each side of the porch roof.
Set the Support Posts
Opposite to the ledger board, dig two posts in the ground to the depth required in your area. If your area freezes, you may be required to dig the holes below the frost line. Fill each hole with about four inches of gravel. Set the six-by-six posts plumb in the concrete and let the concrete fully cure.
Notch the Support Posts
After measuring with the Speed Square, cut down the support posts to the height required for the porch roof to be at the desired pitch.
Next, with the circular saw and manual saw, notch out the tops of the support posts to receive the two-by-ten header beam. The notch dimensions should be 1-1/2-inch deep by 9-1/2-inch high.
Attach the Header Beam
First drill pilot holes, then use lag screws and washers to attach the header beam to the support posts in the notches.
Install the Rafters
Install the two-by-six rafters, extending from the rafter hangers to the top of the header beam. Nail the rafters into place through the holes in the rafter hangers. On the beam side, toenail the rafters to the beam.
Attach the Roof Sheathing
Nail the 1/2-inch exterior plywood to the tops of the rafters.
Install the Shingles
Install the shingles to the porch roof. One square of shingles will be sufficient to cover this roof. Start at the bottom of the porch roof. Install rows progressively upward until you reach the side of the house.
Square is a roofing industry term that refers to 100 square feet of shingles.
Attach the Drip Flashing
Nail the strip of drip flashing to the joint between the porch roof and the side of the house. Drip flashing should run over the shingles.
Install the Siding
Install the siding. The siding should run over the drip flashing.