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Repairing A Severely Rotted Subfloor

Construction How-To, Flooring Installation, Floors March 15, 2016 Sonia


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After marking the floor plate with a square, our carpenter Chad cut it with a reciprocating saw so the bad section could be replaced and so the subfloor underneath could be removed.

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He used a reciprocating saw with a bi-metal blade to cut through the nails where the studs were connected to the plate.

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He cut the plate up into sections for removal because this plumbing wall had lots of pipes to work around.

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After removing all of the affected wood, Chad made up a strong bleach solution in a spray bottle to kill any remaining mold or fungi.

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He measured and marked out a 4×8 sheet of plywood to replace the damaged subfloor.

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He snapped a chalk line to connect the layout marks, which were centered over a floor joist.

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Following the cutline on the subfloor, Chad used a cat’s paw bar to pull all nails that might be hit with the circular saw blade.

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After removing all of the nails along the cut line, he set the blade depth on the circular saw to cut about 1/16 inch deeper than the shiplap subfloor before cutting along the line.

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He removed the subfloor out to the floor joist beyond the damaged area.

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A shop vac helps to clean out sawdust and other debris in the area under the subfloor.

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Chad placed a pressure-treated 2×6 scab along one of the damaged floor joists to add strength and to provide a solid fastening area. The scab also provides more area for the new subfloor joints.

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He nailed the scab to the existing joist with nails approved by the manufacturer of the treated wood, which has specific fastener requirements.

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Chad positioned the subfloor plywood to go under the wall so he could lay out notches for the pipes in the wall.

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After cutting the notches for the pipes, he positioned the new under-wall subfloor piece to reach the floor joist scab and to leave enough room for the full sheet of plywood subflooring.

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