How to Fix a Rotten Board on a Roof

Damon Hildebrand

Over time, even the best-built roof can form a slow leak if shingles allow moisture to find its way into the decking underneath. The results of a slow leak such as this are usually not evident until the shingles are torn away for replacement.

Does damage lurk under your shingles?

When decking boards are found to have water damage or rot, they can be replaced with little effort if the right tools are available.

  1. Remove the shingles and felt paper from the affected area to fully expose the complete section of roof decking board to be replaced.

  2. Observe the decking board to be removed to determine if it is fastened to the roof rafters with decking screws or nails. The type of fasteners securing the deck will determine the proper tool to be used in order to remove the board.

  3. Remove any nail fasteners in the decking board using a hammer and large nail puller. Drive the nail puller under the nail head using the hammer to get the best bite on the nail. With nail puller in place, pry the nail from the decking board. Since the board is already damaged, no precautions are necessary to prevent damage. Continue this step for all of the nails securing the rotten board to the roof rafters.

  4. Remove any screws found securing the deck board with an electric drill and Philips-head apex tip. A slight clean-out of each screw head may be necessary with a hand-held screwdriver before using the electric drill. Firmly grasp the drill and press downward to prevent stripping the screw head and complicating its removal. Continue this step for all screws found securing the decking board to the roof rafters.

  5. Remove the rotten decking board from the roof once all fasteners have been removed.

  6. Using a standard tape measure, measure the area on the roof from which the board was removed from both length and width. Write these measurements down and subtract 1/16 inch from each of the measurements recorded.

  7. Mark the new board dimensions with a straightedge, using the measurements recorded. Using a circular saw and saw horses, cut the new board to the exact dimension drawn with the straightedge. Double-check the measurement after the cut to ensure the proper dimensions have been obtained.

  8. Place the new board in the space on the roof and secure it into place with 1½-inch decking screws at all four corners.

  9. Replace the roofing felt over the new roof decking board with new felt, and secure it with felt tacks. Install new shingles over the felt.

  10. Tip

    Use the same type and grade of lumber for the replacement decking board as was originally used to ensure a flat, even surface.


    Always use extreme caution when working on a roof to avoid slips, trips, and falls.

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