Q: About a year and a half ago we bought and moved into a 13-year-old frame house. After moving in we discovered that a 3-by-3-foot area near the center of the bedroom floor squeaks when we walk on it. The room is fully carpeted. The crawl space below is 16 to 20 inches high. The floor is insulated with batting held in place with plastic netting. How can we stop the squeaking?
A: There’s good news, better news and some not-so-good news. The good news is that we’re confident you can fix the squeak. The better news is that it won’t cost much, if anything. The not-so-good news is that it’s a two-person job and one of you gets to go into the dark, cramped and dirty crawl space and wrestle with a bit of insulation.
We suspect the source of the squeak is a shoddy subfloor nail job. Because the house is relatively new we’re pretty confident that the subfloor is plywood or oriented strand board nailed onto floor joists of either dimensional lumber (2-by-8, for example) or engineered I-joists. The nailing pattern should be every 6 inches on the edges of each sheet and every 12 inches in the field.
These days, carpenters use pneumatic nail guns to fasten the subfloor to the floor joists. Modern construction is built for speed. Gone are the days of the carpenter with a fist full of eight-penny sinkers, slugging away at a floor.
The plus side of these nail guns is that they’re faster. The downside is, well, that they’re faster. With a nail gun it’s easy to miss the mark and just as easy for the gun to run out of nails and the carpenter not know it.
We think your squeak stems from either the nails missing the floor joist in the middle of that 3-foot area or from the carpenter running out of nails and not noticing until he had fired a few blanks. In either case, it’s most likely that there are no nails securing the subfloor to the joist in that area.
Because the squeak is limited to that area, we suspect that only one joist is involved. Fixing the squeak is a simple matter of re-nailing the plywood substrate to the floor joist. The trick is hitting the joist.
To tool up, you’ll need two hammers, 16 ounces or heavier, a flashlight or mechanic’s drop light and a half dozen or so 10d finishing nails. That’s it.
We suggest that you be the one to crawl under the house. After all, it’s your home, so you get to do the dirty work. You’re also the one most likely to make sure the job is done right. Your job will be to tell your helper — spouse, kid, neighbor, whoever — where to nail.
Once under the house, have the helper hit the floor hard with the hammer in the area of the squeak. These thuds will guide you to the right spot while you crawl around in the dirt.
Once you’ve located the general area by sound, remove the insulation from between the floor joists and check for wire or pipes. If all is clear, and we think it will be, have your helper drive a nail into the floor. With luck you’ll spot the nail. She shouldn’t drive the nail all the way through because if she misses you’ll need to drive it back up to her.
If you don’t spot the nail, there’s a good chance you’re looking in the wrong joist bay. Have her pound on the floor again, move in the direction of the sound and remove the insulation. Have her drive another nail. Continue the process until you can see the nail she has just driven.
Once you’ve spotted the nail, tell your helper how to put the next nail into the joist. Simple instructions work best. “About 6 inches toward the front of the house” or “2 inches toward the bathroom.” If she misses again, repeat the process until she sinks one into the joist.
When she has hit the joist, she can continue to nail the subfloor to the joist every 6 inches within the area of the squeak. This is critical. Make sure the finish nails are driven all the way home — through the rug, through the carpet pad and flush with the subfloor. If you don’t, some night on the way to the potty you’ll snag your bare foot on that protruding nail head, and it won’t be a pretty.
Once the floor is fully nailed, test it by having your helper walk on the floor. Both of you should be able to detect any squeaks. Once you’re satisfied that squeak is gone, drive any nails that missed the joist back up through the subfloor, replace the insulation and the netting, get the heck out from under the house, and congratulate yourself on a job well done.