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How to Attach a Patio Roof to an Existing House

When you attach a patio roof to an existing house, you can create a patio look that flows from roof out. Creating this patio roof requires some woodworking knowledge and patients, but if you have the skills and time, you can make it work. Here, our roofing experts explain how to attach a patio roof to an existing house.

  1. Beginning from the roof to the house (not the house to the roof), calculate the sightline clearance height.
  2. After that, determine the beam size you’ll want to use.
  3. Then, choose a roof pitch and roof structure.
  4. Because you’re installing your roof on top of your existing roof, you’ll want to consider whether to remove the existing eave or keep it. (If you decide to remove it, make sure that it won’t compromise the integrity of the overall structure.)
  5. Next, determine how many beams, rafters, and roofing planks you’ll need for your design.
  6. Stain your wood pieces to protect them from outdoor elements.
  7. Then, fasten the post bases to the ground using lag bolts and a screwdriver and make sure they sit plumb.
  8. Cut one side of the horizontal roof beam on an angle so that the rafters sit flush on it.
  9. Using your nail gun, attach the horizontal beam and cut the two outer rafters to sit flush on top of the existing house roof.
  10. Install the two outer rafters and attach a plain rafter beam to the very edge of the existing roof.
  11. As you continue to install your rafters, cut the house end of each one so that it fits over top of the plain rafter beam.
  12. Once all of the rafters are in place, attach your planks horizontally across the rafters to form your patio roof.
  13. If you’re covering the patio roof with shingles that match your existing roof, install black roofing felt and a layer of oriented strand board.
  14. After that, you can attach your roofing shingles.

*Photo courtesy of

Tools & Materials

  • Wooden Beams
  • Rafters
  • Planks
  • Nail Gun, Nails
  • Lag Bolts, Screwdriver
  • Black Roofing Felt
  • Oriented Strand Board
  • Roofing Shingles
  • Ledger
  • Utility Knife

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