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What to do with holes in subfloor before putting down underlayment

Posted: Sat Feb 02, 2019 11:45 am
by BrokeIt
I'm going to tile my kitchen floor and I have a bunch of small holes from various things in the subfloor. Most are fairly small but there is one big one around 2" from an old drain.

I'm using 3/8 ply as underlayment. Do I need to patch these holes first or can I just lay the underlayment on top and have at it?

If so what's the best way to fill them? An other tips and tricks putting down the underlayment?

Re: What to do with holes in subfloor before putting down underlayment

Posted: Sat Feb 02, 2019 12:05 pm
by A. Spruce
I would say you can just cover them with the underlayment and have at it. The only time you might have a problem is if you point load the floor in that exact point, something that is highly unlikely. If you want to fill the hole, you will have to install a backer block, then cut a patch of the same size and install that, then lay the underlayment. I wouldn't worry about anything less than an inch in diameter, and would only worry about the 2" hole if it's out in the main traffic area.

Re: What to do with holes in subfloor before putting down underlayment

Posted: Sat Feb 02, 2019 12:18 pm
by Shannon
Yup I would agree, you should be fine leaving the holes

Re: What to do with holes in subfloor before putting down underlayment

Posted: Thu Feb 14, 2019 10:37 am
by BreakItMore
What's the best way to install the underlayment?

I currently have reg 5/8 plywood (not T&G) for the subfloor. I have 3/8 exterior grade plywood I'm going to use as underlayment then uncoupling membrane with infloor heating and then tile.

The floor used to squeak pretty bad, it was just nailed before, but I've already screwed every 6" and now the squeaks are gone.

What is the proper way to put down the underlayment? My current plan is to put down the 3/8 ply offsetting the subfloor joints. Keep a 1/8th gap between the sheets of underlayment and only screw the underlayment to the subfloor, not through to the joists. Is this the proper method? Should I leave the gap between sheets? Should I also glue the underlayment down?

Any other tips or advice I'd love to hear it. Thanks!

Re: What to do with holes in subfloor before putting down underlayment

Posted: Thu Feb 14, 2019 6:35 pm
by Shannon
So will 5/8 ply and 3/8" ply with the spacing of your joists satisfy the requirements for the manufacture of the membrane? if your joists are over 16" O.C it likely does not.