cement floor slopes up

I want to install flooring in fairly large room but first their is a corner of the room that slopes up aproximately 3 by 4 feet
how do I level the cement? Can the corner be shaved down or must the whole large floor be raised?

 

I have to say your opportunity for a level floor has passed. Oh sure, you can rent a concrete floor grinder but apply one in your situation and I'm sure you will find that the juice is not worth the squeeze. Have you ever seen the dust they create. For my money, you may have to just live with this snafu. Sorry.

bs5

 

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MY SUGGESTION: I just leveled my own basement floor that had sunken badly over the years. It was low (.5" to 2.75") in various spots from 10 ft. to 15 ft. long and involved about 75sq. ft. of areas that had to be raised up to level out the floor.

You have the opposite problem, and I assume your floor is reasonably level other than the high spot in the corner. You coud rent a small jack hammer to remove the excess concrete just below level (maybe by about 3/4" to 1"), and then fill in, level, and smooth out the area with concrete patch that is recommended for shallow repair work. Also incorporate a concrete adhesive in the mix to insure good adhesion between the old and new concrete).

You can then carpet the room, although you might want to first apply a concrete water-proof paint (2 coats are always recommended) over the entire room.

If you want a subfloor to support a real hardwood floor, for example, I suggest 2x6's ("treated" lumber) lying FLAT 12" on center to create a very solid base, or the standard 16" on center. Nail them down into the concrete floor. You must rent a nailing gun appropriate for this purpose. Do the perimeter of the room first, then position the rest of the
2x6's. Use about six 2-1/2"-long nails per 8ftr.

Once the 2x6's are all secured, check your floor with your 4 ft. (minimum length) level-- in all directions. You can shim (lift up) any low spots using thin, hard plywood strips (1/8", 1/4", or 1/2" thick, by 5-1/2" wide) to raise those low spots as needed-- just nail these strips onto the surface of the treated lumber (four one-inch nails are sufficient), and use your level as you go. But be sure there is no more than 16" between these shims, otherwise you could experience some "bounce" between the shimmed portions and the subfloor; that's why I would use 12" on center.

When done, place a long, true straight edge over the 2x6's is various directions (and on top of the shims) to be sure the floor is level from all angles. Place your level on top of this straight edge. Look for spaces under the straight edge. You might have to fill in other spots with shims to prevent any discernible bouncing of the floor. (Maintain no more than 12" of empty space between shims).

Then attach the 3/4" thick tongue-in-groove plywood sheets (use "real" wood) to form your subfloor. Note: Lay the plywood sheets so that the grain runs "across" the 2x6's in the opposite direction. Nail them to the 2x6's with 1-1/2" long flooring nails-- or apply 1-1/2" screws using a screw gun. Noter: Use heavy-duty construction wood glue (apply to the 2x6's only) in addition the nails or screws; this helps reduce the chance of any possible bouncing. Apply one sheet at a time, and don't nail too closely to the "tongue" edge of the sheet since the next sheet has to slide tight all the way into the "groove." You can go back later and nail closer to ther edges. Use sufficient nails (or screws, which are more effective) to be sure the sheets are securely nailed down and that the plywood edges match up to each other at the seams.

Then you can finish the floor as you like-- with hardwood, carpet, etc. Tile or certain linoleum-type products would probably require filler coatings to cover nail holes and seams.