Greetings all. My first post... I have 3/4" red oak flooring that is ready to be nailed into my OSB (I assume 3/4" thick) subfloor. However before I start I have a serious problem:

I recently ripped out the old vinyl flooring in my kitchen, dining room, and sunroom. The rooms are on the 2nd floor of the townhouse. I've discovered that there is about a 3/8 inch dip in the floor that runs parallel to a few joists in the dining room. The rest of the floor in the rooms is pretty flat. At least flat enough to fall within the 3/16" over a 10 foot span. However, the dip in the dining room is 3/8 of an inch over approx a 6 foot span and about 11 feet long. (Deepest part is 3/8" in the middle with it tapering up as you get about 6 feet wide). This is well above the acceptable variance of the floor. My question is, how can I correct this? I read a recommendation of using roof shingles but I suspect this is for a more minor variance in height. Do I try to get a sheet of plywood and lay it down? If so, how do I taper the edges? I'm really stumped and it seem like the dip is too deep for roof shingles and too big and deep for floor level compound.

Thanks for your help.

Travis

For deep depressions such as this I like to use a combination of fillers. First using wood as much as possible. And vinyl scraps upto 3/16", and then feathering with a high quallity grey tile thinset or latex fortified cement filler to smooth.