Repairing Your Plywood Subfloor

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Repairing Your Plywood Subfloor

If your home has a basement or is built off the ground with post-and-pier supports, you probably have some plywood subflooring. The usual culprit causing rotted plywood subflooring is water damage. Given that fact, you would expect it in your kitchen or bathroom. Do you find yourself in this unlucky position? Why not repair your plywood subflooring yourself?

Tool and Material List

Here’s what you’ll need for this project:

  • pry bar (for old tack strips if you have them)
  • hammer
  • chalk line
  • measuring tape
  • utility knife
  • circular saw
  • chisel
  • screws or nails
  • plywood
  • wood putty

Remove the Current Finish Floor

In most cases the whole subfloor doesn’t need repair, only limited areas. To determine this you will have to remove your current finish floor, whether it’s sheet vinyl, carpet, or something else. It’s a great time for remodeling anyhow.

But prior to doing anything, give your homeowner insurance agent a call to review your situation and file an insurance claim. If you’re covered and you do the repair yourself, you’ll save all the labor costs that will they will pay you for.

If carpet is what you have and it still has some life left, you can undo it from the tack strip and roll it up to reuse. If not, just get rid of it and the padding.

Take Note of your Damage and Prep the Area

Now take a look at your plywood subfloor. Make a note of which areas need repair. Do a visual inspection and poke it with something sharp to test for mushy spots. When you’ve found the bad spots that need repair, strike chalk lines so you’ll know where to cut.

Keep two things in mind: the spots marked off must be square. Use the 3-4-5 rule to ensure this. Secondly, any cut you make parallel to a floor joist must be down the nearest joist’s center line. Strike your chalk line centered on the existing nail heads.

Cut Out the Damaged Subfloor

Use an electrical circular saw to remove the damaged spots. Prior to cutting, look at the underside of your subfloor if you can from the basement, to prevent cutting through electrical wiring or plumbing. Set your blade cutting depth just one 1/4” deeper than the damaged plywood subfloor.

When you close in on a wall you’ll find that the bottom plate of your circular saw will prevent you from reaching the wall. It’s time to use your hammer and chisel.

Replace the Damaged Plywood

Now that the bad plywood is gone you can install the new. There are two things to consider: the thickness of the existing plywood and the amount of new plywood you’ll need to buy. Plywood is sold in 4′ X 8′ sheets so you’ll need to buy a little extra to account for scrap.

When you get the new plywood home the rest is easy: taking measurements, cutting the sheets, and installing them. Drywall screws with coarse threads are good for this project. In the old days, subfloors were were nailed down but nails work loose.

Today, responsible building contractors apply construction adhesive to the floor joists before screwing.

When you’re done, putty the gaps.

You might need to scrape or sand your old subfloor. Now it’s time to install the new finish floor… but that’s another project!

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