According to the American Plywood Association and The Engineered Wood Association, there are 11 causes of subfloor squeaks. Most solutions take reasonable time and money to correct. While in extreme cases correcting the problem can take more advanced techniques and be more costly, it is very rare that an entire floor will have to be replaced. Listed below are the 11 causes of subfloor squeaks and their solutions.

#1) PROBLEM:

WET OR GREEN LUMBER
Wet or green lumber (greater than 19%) will normally dry to 6-12%. As lumber dries, the boards begin to shrink, while the nail stays in place. Another effect of wet lumber drying is a gap that appears between the panel floor and joist.

SOLUTION:

Place a heavy object on top of the area that squeaks, then take a 2-3ft long piece of pre-drilled lumber or metal angle and attach it to both the panel and floor joist with sheet metal screws. If the floor joist is inaccessible, place a heavy object near the nail that has “popped” up. Once the nail has been located, drive it home with a 3/16′ drift punch (vinyl- cover the punch with a piece of card board for protection). If the nail cannot be located, find the joist, punch hole with an awl (vinyl- cut three sides of a square with a utility knife), hold carpet fibers away from hole with masking tape, then pre-drill and nail into the joist.

PREVENTION:

Use dry lumber for the subfloor. Also, using deformed shank nails of the shortest length possible in the required pennyweight will increase holding power.

#2) PROBLEM:

IMPROPER PANELSPACING
During the construction of a house and during different seasons, floor panels will expand slightly because of high levels of moisture. If these panels are not spaced according to APA recommendations, there will be no room to expand and buckling will occur.

SOLUTION:

Follow instructions in solution for cause #1.

PREVENTION:

Follow the APA recommendations and use proper fastener types, sizes and spacing.

#3) PROBLEM:

IMPROPERLY GLUED FLOOR
If proper instructions are not followed during the gluing process, and several panels are glued at one time, the glue will harden before the nails can be driven. This results not only in a poor adhesive bond, but also in built-in gaps as the panel hangs on uneven beads or lumps in the glue.

SOLUTION:

Follow instructions in solution for cause #1.

PREVENTION:

Follow the APA guidelines for properly glued floor construction methods.

#4) PROBLEM:

IMPROPERLY DRIVEN NAILS
While power nailing does increase speed, it also makes it harder for the operator to tell if they have missed a joist. A nail that barely misses or hits the joist will not hold the panel flat against the joist. As a result, the panel will deflect and the nail will rub on the joist causing the floor to squeak.

SOLUTION:
If there is access to the joist space, bend the nail away from the joist and re-nail where possible.

PREVENTION:

After nailing, inspect joists and replace nails that miss.

#5) PROBLEM:

BLOCKING AND BRIDGING
When blocking and bridging is not nailed correctly and securely at the bottom, it does not transfer the load to the adjacent joists. Rather, it slides or rotates. This rubbing on the joists causes a floor squeak.

SOLUTION:
Make sure the adjacent diagonal bridging members will not contact each other there they cross. Securely nail the bottom of the blocking or bridging and completely renail it.

PREVENTION:
Provide space between pairs of bridging members to ensure they will not contact each other and securely nail the bottom after the rough structure is in place.

#6) PROBLEM:

INTERIOR WALL PARTITION
At the point where a wall meets the floor, it is common practice to nail the lower plate of the interior of the wall to the panel instead of the joist. When a floor settles, the subfloor can rub on the nail shank and cause a squeak.

SOLUTION:

Use clinch nails to penetrate the panel subfloor or drive screws up through the subfloor into the lower plate. Diagonal can also be inserted under the partition.

PREVENTION:

Nail lower plate only where it crosses the joist. Also, a bead of construction adhesive along the bottom plate may help.

#7) PROBLEM:

JOIST HANGERS
If a joist is not fastened to a hanger or is only fastened at the top, as the lumber dries it will shrink away from the base of the hanger. When this happens, the joist will move freely in the hanger and squeak when the parts rub together.

SOLUTION:
Place a tapered shim between the joist and the base of the hanger. Also, nail the bottom of the joist through the holes provided.

PREVENTION:

Use dry lumber, make sure the joist is properly seated in the hanger, and fasten at both the top and bottom through the holes provided.

#8) PROBLEM:

SUBFLOOR, UNDERLAYMENT, OR FINISH WOOD FLOORING CONNECTION
If the connection between the subfloor and underlayment is not adequate, the underlayment panel can slide up and down on the nail shank and cause squeaking.

SOLUTION:

Select a screw length for maximum penetration, but that will not penetrate the surface of the floor. Then, from the joist, drive the screw through the subfloor into the underlayment.

PREVENTION:

Sweep the subfloor before installing underlayment, use APA recommended fasteners, and use underlayment adhesive.

#9) PROBLEM:

CEMENT-COATED NAILS
Initially, cement-coated nails increase holding power, but eventually the coating can break away from the nail shank. This will cause a weaker connection and the potential for a floor squeak.

SOLUTION:

Refer to solution #1.

PREVENTION:

Never use cement-coated nails. Instead, used deformed-shank nails.

#10) PROBLEM:

DUCTWORK
When a hole has been cut too closely for heating vents, or the heat from the vents cause increased drying in the panels, this can cause squeaks.

SOLUTION:

Provide clearance or insulate between the floor element and the ductwork.

PREVENTION:

Make a larger hole during installation of ductwork.

#11) PROBLEM:

VARIATION IN JOIST DEPTH OR STRAIGHTNESS
Because of variability of wood and because lumber will shrink as it dries, this can cause differences of joist depth. When the floor is subjected to floor traffic, it loosens the connection and allows the panel to slide up and down along the nail shank.

SOLUTION:

Refer to solution #1.

PREVENTION:

Stand over the joist to ensure contact. If the joist id curved or crooked, install it with the crown oriented upward.