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How to Fix a Collapsed Roof

Billy McCarley

When a roof collapses, it often is because there was not enough support underneath it, either from rot or failure to build correctly. When the weight above the roof becomes too much, the structure will collapse. If the collapse doesn't involve the entire roof, then you may be able to repair it.

Cover the Roof

Roof Damage
  1. To minimize the damage, cover the collapsed area with a tarp. Determine how much you need by allowing for five to 10 feet of coverage past the damage. Tie the tarp down with bungee cords or rope, usually at the roof overhangs, just beyond the damage, until repair begins. Keep the tarp handy while working in case of unexpected rain.

  2. Ready for Repairs
  3. Rip off any loose materials that were left behind and hanging. Cut through and remove partially attached 2-by-6 and 2-by-8 rafters. Once the collapsed area is free and clear of all loose and damaged debris, you can begin reconstruction.

  4. Replace or repair any broken rafter. Usually, you can add a patch onto any broken rafters using a 2-by-4 of appropriate size depending on rafter sizes. Have a helper apply pressure against the broken rafter while you place the 4-foot patch against the broken rafter and insert screws to secure it into place. It may be necessary to apply a double patch, one on both sides of the broken rafter.

  5. Replace Roof Decking
  6. Replace roof decking with 4-by-8-by-1/2 Oriented Strand Board, or OSB, sheathing or desired exterior plywood. To determine the amount you need, multiply the length by the width of the area to be covered and divide that by 32. Use 8 penny nails to secure to roof framing.

  7. Final Roofing
  8. Cover the exposed area of wood with 15-pound felt paper and secure with orange-cap felt nails. Reshingle the area. Determine the amount of shingles you need by multiplying the area's length by its width. One bundle of shingles equals 33 square feet. Make sure the shingles overlap correctly and follow the installation instructions on the cover.