Removing a piece of OSB subflooring
05 February 2020

QUESTION
I need to remove a piece of tongue and groove OSB subflooring panel to get some wiring through to my attic. What’s the best way of doing this?

ANSWER
If the T&G OSB subflooring panel has been screwed in place, you will find that you are easily able to remove a piece of the OSB subflooring panel. If the subflooring has been glued and nailed into place, this will make matters more difficult. In this instance, you may want to consider making holes through the ceiling below and through the subflooring to feed the cables through.

If removing a piece of the OSB subflooring is the only option, use a circular saw to make a cut down the long edge of the T&G between the sheets of subflooring. Make the cut 1/8 inch less than the thickness of the OSB subflooring to prevent cutting the attic floor joist or truss bottom cord. Not doing so could lead to damage to the wood framing.

Cut the T&G on the two long edges, carefully remove the fasteners and gently pry the OSB subfloor panel from the floor joists using a crowbar. Do this carefully so that if you have missed a nail, it won’t damage the panel.

If glue has been used, you may need to cut out each rectangle of the OSB panel between the floor joists rather than removing the whole piece.

After you have completed your wiring, cut and nail pieces of wood blocking under the longest edge of the subflooring to replace the tongue you cut when removing the panel.

This process will also create a good opportunity for you to maintain the insulation in your flooring whilst you have the panel removed.

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