Subfloor leveling ideas for shimming

For small areas and thicknesses I use vinyl scraps (paper backed or inlaid materials) much the same way one would use shingles or felt.
I have also used cedar shakes.

 

I install vinyl flooring. The scraps are from those jobs. I try to use commercial inlaid material as these will compress less than felt.

 

Knowing what I know now, that's a floor for Uzin 172. Seal the cracks and pour it on.

 

you glue it...

 

Good work mapping out the flatness requirements on that PDF. That is the tricky part over with.
The way I would approach that is to use sheets of door skin (1/8" plywood) Common and inexpensive around here (hopefully in your area as well). It can usually be cut to size with a utility knife, and layered on the low spots as necessary. You will end up with what looks like a topographical map on your subfloor. Just keep going until you have eliminated the gaps under a 10' straightedge - check in each direction. You can staple or nail them in place as you go, or bond it all with a construction adhesive. Once you have flattened your subfloor, you are ready to install the new underlayment (really wish you had gone with a t&G plywood instead of OSB, but we can't win em all)

As stated above, flat is more important than level for your application. Hope that helps. Let us know how you manage.

Cheers,
G

 

Doorskins are usually mahogony or other wood. They are a ply style panel. The disadvantages of OSB subfloor are only apparent when trying to nail into it. The OSB has poor holding strength compared to a plywood and in the long term does not hold up as well. That being said, many a million of square feet of hardwood is installed every year on the stuff and it is generally accepted however it is always preferred to use Ply. Do yourself a test, when the time comes, nail a test board into the osb, then find a scrap of 5/8 plywood and nail into that, then try and remove the two boards by prying on them from the tongue side up. You will understand.

 

Where do you get doorskin material? I can't think of any place around me (Nashville TN) to even look. Millwork houses, what kind of places do you get it from?

 

Any lumber yard will have something in a 1/8 sheet. Here i buy "bintangor" or rotary mahogany as it is referred to for some reason... neither seems true... Really all you are looking for is something in 1/8 ply style, 3/16 will work in a pinch, but it is more work to sand

 

Ah, 1/8, I missed that clearly stated detail and went off searching for something thinner. It was the "cut it with a utility knife" that misdirected me brain. My 1/8 ply isn't that friendly LOL. Anyway 1/8 ply is pretty available I think. So your practice is to "topo" it then sand the skins? Not to derail the thread, but I had envisioned, in the case of a "bowl depression" for examples sake, a small disc at the bottom of the bowl, then a larger disc, then a larger one and so on. Trim the "bowl"'s last layer with patch around the edges depending on what's going on top. Presuming I got that wrong, can you elaborate on your method? Thanks for chiming in.

 

Some great information! I have the same issue in a 16x28 room where I have a 2 1/2 inch drop among the front wall. I was thinking of building custom shims and then adding 1 1/8 T&G plywood. I will then be gluing 3/4 engineered hardwood. I'm thinking this is easier than ripping out 1x8 boards that make up the subfloor now and then adding new 2x12's to level the floor.