Gary must have been talking about my subfloor - "MAJOR subfloor problems in term of being flat; forget trying to be level. These floors are dropping 1&1/2" in 4 ft. How the hell can I fix that without causing other issues like transitions to other floors, appliances, cabinets, etc. So the answer, unfortunately, is a comprimise. Raise the low spots up as high as possible without causing a major problem with the transitions to other floors."

So when I remove the 800 square feet of carpet I find this old spongey 1/2" plywood subfloor in poor shape. So I figure I'll just screw down a new 3/4" plywwod subfloor on top of the old. Not so fast! I have a 1" to 1 1/2" drop in 4 feet here and there.

Is putting 3/4" plywood over the old subfloor even a good idea. Do I use layered shingles to shim up wherever it needs it?

What's the best way to proceed?

Thanks for your help!

Mike

You got a mess . Going up 1 1/2" is too much for filler materials. You will probably need to remove the subfloor and see whats going on. If the joist are not cracked, split or fell down off the ledger you may can sister on new joist to bring it up.

This is a problem someone needs to look at on-site.