How Do I Find Joists Under Carpet?
Q: "How do I find joists under the carpet to fix a floor squeak?"
My carpeted floors squeak, so I'd like to screw the loose subfloor to the floor joists from above using one of those special screws with the snap-off heads. But how do I find the joists under the carpet?
— Harold, Glen Carbon, IL
Tom Silva replies: It's not hard. Wall-to-wall carpeting is held in place with tack strip nailed to the subfloor around the perimeter of the room. To free an edge, grip the carpet at a corner with pliers and pull up. Then peel back a small area of pad to look at the subfloor. Once you find two rows of nails, you'll know how far apart the joists are spaced and can measure to find the ones that squeak. (Joists are usually spaced 16 inches on center.) Tuck the carpet edge back under the baseboard with a stiff putty knife. Now you can screw the subfloor to the joists, following the instructions provided with this screw system.
There's a risk to this approach: Some types of pile may catch on the screw as it's being driven in and tear the carpet. Also, on short-napped carpet, you may see the screw holes when you're done.
The safest approach — the one I'd use if it were my house — would be to rip up the carpeting and the pad completely, screw down the subfloor with deck screws, and hire a pro to put everything back.