Fixing a Squeaky Floor

Floor squeaks can be caused by things other than the connection between the subfloor and the joists. You can read about that in our other article: How to Build a Squeak-Free Floor. Most houses are built using floor joists that meet the building code minimum for spacing, size and span but still flex when you walk across them. Remember, the building code that your builder used is a minimum requirement, not the ideal requirement. Floor joists can flex from the weight of furniture and people walking and still safely support the weight for the life of the building. When the floor joists flex down and spring back several things can squeak.

First, you need to know that the connection at the end of the joist or where it sits on its support, is nailed or toe nailed in place, and can cause squeaks. Sometimes you have blocking between the joists at the end and/or they could be nailed to a perpendicular rim joist. All of these components are nailed to each other. As the joist flexes the connecting nails at the ends and the wood can move slightly rubbing against each other.

A second issue is the row of bridging that may be installed between joists at the midpoint of their span or at 10 foot intervals to prevent twisting of the joists and basically stiffen the floor. If the carpenter used blocks of wood for bridging, the wood shrinks a little and the nails holding them in place work loose a little, causing squeaks as the nails rub against the wood or the wood rubs against other wood. Some bridging is built using 1x lumber nailed between the top and bottom of joists that looks like an "X" from the side, called X-bracing. Squeaks can occur when each piece of the X-bracing is not spaced apart where they cross, or the fasteners may be the problem again.

The third is caused by interior walls resting on the floor that "squeaks". When an interior wall is framed on top of a subfloor, nails are driven through the bottom plate of the wall into the subfloor (and hopefully into the joists.) Depending on where the wall is located in relation to the supports under the floor, the nails at the bottom of the wall can come loose over time. When the floor flexes up and down the nails on the bottom of the wall rub against wood. This can cause a popping or squeaking sound.

The fourth situation is where floor joists overlap. If the subject floor is a second floor, the joists often span across two rooms below. The joists from each room often rest on the same wall and must overlap each other. The overlap is typically nailed together and the joists are toe-nailed to the top plate of the wall they are bearing on. It doesn't take much of an imagination to realize nails and wood are going to rub against each other giving the right amount of flexing when you walk on the adjacent floor. By the way, if the squeaky floor is over a crawl space or basement, the same situation applies except instead of a wall below you may have beams holding up the floor (instead of walls).

The last ones are heating ducts and pipes installed within the floor framing system. When you walk across the floor the movement from your weight can cause the floor framing to move and may cause the duct to flex or rub against the framing. Pipes are often attached to floor framing and/or they pass through holes drilled in the joists. Any flexing of the floor could translate into squeaks when the pipe rubs on wood or against its own supporting device.

What to do?
You will need to determine exactly where the squeaking sound is coming from. Based on the four typical areas where floors squeak due to framing:

If you have thoroughly screwed down the subfloor to the joists, try driving a nail or nails into the floor in the area of the squeak between the joist locations. If you find resistance, like driving into wood, determine the extent of the wood which might be a block or bridging. Add screws until the squeak stops or you run out of places to put screws 3 to 4 inches apart. Make sure the screws are long enough to penetrate the joist at least 1 inch. Don’t use screws much longer than this or you may puncture mechanical or electrical items in the floor.

Try temporarily laying a sheet of 3/8 or 1/2 inch plywood or OSB (oriented strand board) over the area that squeaks and see if that helps. The wood panel will help distribute the weight over a larger area of the floor, minimizing the deflection and therefore not causing the movement that caused the squeak to begin with. The solution, though not cheap, would be to fasten down underlayment over the entire floor. Make sure you screw the fasteners for the underlayment all the way down into the joists with at least 1 inch penetration.

If you suspect that ducts or pipes pass through the floor system and are causing the problem, they must be exposed in order to duplicate the squeak and isolate where it is coming from. Pipes and ducts can be cushioned from their supports and otherwise isolated from the any rubbing surface. Some people use a cheap stethoscope-like device to narrow down to the exact location.

All other solutions are going to require cutting major holes in either the floor or the ceiling below to expose the framing. The framing repairs or modifications should only be done by a qualified carpenter under the direction of a qualified contractor.