My sisters house has got lovely oak hardwood floors that are loosing the battle against time and her 3 now teenaged kids. One board in particular by the landing of the stairs has a piece broken off on the end. Kind of snapped about an inch from the joist it sat on. Ther are other spots like this, either in high traffic areas or where the board ends have a wild grain shift. I was thinking of cutting 1/2″ CDX to slip up between the basement joists(and pipes, and wires….) , and glueing and screwing it to the underside of the floor. I figured 5/8″ screws countersinking into the CDX would get me to a point where the plywood would support the floor and leave room to cut it again for refinishing. My ? is about gluing it. Would a watebased adhesive migrate up, pushing the finish off the floor above? Should I just trowel on construction adhesive? Shouls I just screen all my calls and not return hers?
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What you describe is sort of like a subfloor dropped in between the joists, as is done when you want extra room for a mortarbed for a tile floor. In that case, the plywood is supported by 1x ledgers nailed to the sides of the joists. You might be a lot better off doing it that way rather than depending on shallow screw tips in the old oak to hold everything up. The ledgers could also be screwed in place, but use good structural screws like from McFeeley's, never drywall screws. Because you're working from below, screws might be better than nails because the nails would have to be angled in the wrong direction to resist the vertical load.
Gluing to the bottom of the oak will earn you the eternal curses of anybody who has to make repairs to it in the future. Put a layer of roofing felt or building paper between the oak and the plywood to prevent squeaking, and depend on good strong ledgers to hold the whole works up. Yellow woodworking glue on the tops of the ledgers to hold them to the plywood, however, would be a good idea. I'd also go thicker than 1/2", probably 3/4".
-- J.S.
I would do just what you are proposing, using PL Premium construction adhesive. I have been cursed by those who follow after me when an owner changes their mind about what they want. That would be the appropriate time to let the machine screen your calls.
Excellence is its own reward!
My first thought is that 1/2" isn't thick enough. If you are going to do this, use something thicker that will really give some support.
Also, I'm not sure I would use any adhesive. It will be interesting to see what the experts say.
If I was doing this (and ignoring the reference to pipes and wires), I would cut the CDX to fit between the studs and push it up against the floor, then I would nail 2x4 to the joists tight up against the new subfloor. Then maybe some screws/nails angled through the 2x4 into the subfloor.
But I'm just guessing.
Another day, another tool.
for times sake... i think i'd use 3/4 decking ply or osb (i'd use osb) and use 2x2 on each side with liquid nails on top & side (so they glue to the osb & floor joist) and i'd use a ring shank nail and nail gun... i would use the felt paper on top... or the glue