I try to drive 1.25" plywood screws through the sub-flooring (5/8" thickness) into the joists to quiet the squeaks. The questions is 1)how to locate the floor joist ? 2)Between the floor joist, there may be water pipe, heating duct etc. How far of those things away from the sub-flooring? Is there a chance that I may hit the pipes if I miss the floor joist ?
Answer:
Depending on how your house was built, yes there is every chance you'll hit wires and ducts and plumbing. The properly built house, of course, will have all these things at least an inch and a half fromt he sub-flooring. My system is to follow the row of nails or whatever other fastener was used to re-enforce the sub-flooring with screws. With 2-1/2" spiral finishing nails on the other hand, I probe for the joist with the first nail and when I've found one, I place a tumbler over it to make sure I don't kneel on it. Using that as a point of departure, I'll find the parallel joists 12", 16", or more recently 19" away. The finishing nails are driven in every 3 or 4 inches along each joist until the squeaks stop. The tumbler is removed when I've done all the nailing I planned to do.
