How to even out a patched-in plywood floor
 

Hello,

I am helping a friend with his bathroom floor. They had a leak, he cut out a 2-foot square section of the plywood, we patched it back in but the old and new plywood does not match up perfectly. In some spots the new plywood is too low. The flooring they are going to install is this thin linoleum stuff so we need to even the subfloor out fairly well.

What should we use? Is there something similar to sheetrock mud? I have seen stuff that you poor on but this is around a toilet so there are holes, I don't think that this liquid stuff would work. Is there soemthing you can put on with a trowel?

I used this product for the same purpose and it worked really well.

Great. Thanks guys.

Well I would use a cemetious based floor patch and then 1/4" underlayment grade plywood. Oh, I am an Armstrong certified vinyl installer. Been doing it for 40 years.

Absolutely you need a cementitious patch and then an approved underlayment. Resilient flooring does not get installed over the subfloor.

Jaz

The cementitious stuff being brittle will fragment when flexed by the weight of people. Is this OK?

Since Linoleum is not brittle or inflexible, I'd put shims underneath the plywood if that area is accessible.
Glueing shoebox cardboard on top of the plywood and sanding flat and level may also work but you should topcoat the cardboard with some waterproofing, like polyurethane/varnish/old paint, then whatever Linoleum needs to have, to bond to.

Leveling within 1/16" is close enough, right?

Where would you get that idea? That's why you don't used gypsum based, it is brittle. Cementious based is not. I have been installing resilient flooring since 1973. Believe me, I have installed stuff that cost $50-$80 a sq yd, using cementious based with 1/4" underlayment grade plywood with no failure.

From here

ce·men·ti·tious
/ˌsēmenˈtiSHəs/
Adjective
Of the nature of cement: "a high-strength cementitious mortar that set within 1.5 hours".

I stand corrected.

Could it be used in mobile home that is not on a slab, but has been leveled last year? Is there a chance to crack in that condition?

Thanks