I'm installing an engineered wood floor in a second floor bedroom. Currently has a plywood subfloor in fairly decent shape. However there are some voids and gaps in the subfloor. What product should be used to fill these areas? Would ceramic tile adhesive work? Do the gaps between plywood sheets (maybe 1/8 gap) need to be taped and filled?Thanks?
You shouldn't have to worry about gaps that small. just make sure floor is pretty level.
They make a type of foam you can roll out on the floor which will fill most gaps and make the floor sound less hollow. (if it's a floating floor) Note: if you use this, you cant glue the floor down. As always read manufacturers specifications.
Do NOT fill the gaps between the sheets of plywood! These need to be there to allow for wood expansion. In fact, if you don't have those gaps, run a circular saw, set at 3/4, down all the joints to open them up. With out this gap, if the plywood swells, it will buckle up at the joints. Voids in the subfloor like knot holes in the top ply aren't an issue. But dips and high spots are an issue. Make sure all the nail heads are flush (and add deck screws if there are any loose spots). Your flooring instructions should list the maximum dip/rise in a given run. If you've got low spots (cr@py carpenter didn't crown all the joists), you can cut pieces of roofing felt to fill in the void. If it takes several layers, feather them with progressively larger pieces, just like you'd feather a drywall joint. High spots can be taken down with a grinder or belt sander with 40 grit paper If you've got a floor with a lot of dips and rises, you can use a self leveling cement to bring it level. It's very thin, like a runny milkshake, and you spread a thin layer with a large floor squeegee. It's thin enough that it finds it's own level, puddling in the low spots. This is typically only needed for tile, but you could do it for wood/laminate.over a really bad subfloor
