I have standard subfloor + 1/2" plywood on top, to correct for joists going different directions, so that all hardwood boards can be laid one direction for a clean look and avoid sagging where they would go parallel to the joists. The sagging problem apparently solved – but would it still make sense to go through the expense of quality underlayment? Or the extra layer of plywood be just as adequate for sound/vapor/heat control? Thanks
Wood – Does it make sense to put quality (=pricy) underlayment over 3/4“ subfloor+1/2” extra plywood layer
hardwoodplywoodsubfloorunderlayment
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If possible, try framing out the edges. I would remove all of the existing sub floor (since it is particle board) and then add addition framing along the edges as needed for the new plywood. In cases where you can't meet a joist, go perpindicular and create a nice foundation for the floor to attach too.
I would make sure the floor has a firm foundation. It might be extra work to do it, but I would take those extra steps if possible.
One solution is to cut subfloor on either side of the offending joist, plane the joist down, sister 2x6 nailers alongside the perimeter of the exposed opening. Then replace the subfloor with new 3/4 ply.
Best Answer
I would. I put underlayment for all engineered. I spend about .25 a sq/ft for my high quality rolls so not sure what you are looking at. The point of the underlayment for engineered flooring is to provide a surface for the wood to slide across (wood on wood gets stuck sometimes) and to decrease the noise between hardwood and subfloor.
Imagining your situation I feel like you might hear Clydesdale clicking and clacking if you don't install anything.