Patch Holes in Subfloor (or Drywall)

As much as we adore our furry friends, sometimes  they make a mess. One of the biggest messes any of our dogs ever made was the time she knocked over a lit floor lamp, which somehow managed to stay lit instead of shattering. It took some time, but the 150-watt bulb melted clear through the carpet and pad, eventually charring a perfectly circular three-inch hole in the subflooring of our upstairs. We came home to a house filled with smoke and a two Labradors cowering in the back yard – no flames, though, so no visit from the fire department.

So… how do you patch a hole in the floor? Well, here’s how I did it…

Tools and Materials

Utility knife
Square and pencil
Jig Saw
Scrap wood for braces
Scrap OSB for patch
Woodworkers glue
Deck or subflooring screws

Step 1 – Evaluate

The burned area was a circular area about 3” across, which (thankfully) didn’t involve a joist. The carpet and padding will obviously need to be patched, but first to patch that hole.

Step 2 – Clear a Space

I cut the carpet and padding back to form a square around 5” on a side, being careful not to cut across the carpet weave. It’d be a lot easier with shag, but my PO bought (cheap) berber for this room.

Step 3 – Cut Away the Char

I cut a square just slightly larger than the outline of the charred area (you can still see some dark spots at the edges) with a jig saw. Now would be a good time to stick a shop vac in the hole to clean out the crumbs.

Step 4 – Cut Some Braces

I cut two strips an inch wide and maybe eight inches long from some scrap lumber. These will act as “fill-in” floor joists for a patch I’ll cut from a scrap of OSB.

Step 5 – Install the BracesI buttered the ends of the braces with woodworkers glue and drilled starter holes through the existing subfloor. Then I held the braces (glue side up!) in place by hand and screwed them in tight with some deck or subflooring screws.

Step 6 – Insert the Patch

I cut a patch to fit the hole from scrap OSB (you could also use plywood or other lumber) and drilled starter holes in the corners of the patch. I applied a bead of glue to each brace, and screwed the patch down securely. Just like that, the patch was done.





We’ll get to the carpet repair some other time.

Parting Observations

• This obviously won’t work for large holes, and the technique is definitely unsuitable for visible patches. Since this hole was small and the patch will be hidden under a patch of carpet, though, it works well.
• This same technique is excellent for patching holes in drywall. You can use short pieces of lath for the backing braces and then tape and mud the seams afterward.
• A slick trick is to cut your patch first and then use it as a template to make the hole: the two will be almost exactly the same size and shape.

copyright © 2014-2020 scmrak