There is nothing that will destroy a customer’s confidence in the flooring installation of hardwood faster than an annoying “squeak”. Many times the blame falls on the hardwood flooring retailer, when it is really something that is out of their control. The following are a few of the causes of squeaks in new hardwood flooring installations:
1) Improper subfloor or underlayment spacing – Floor panels will expand slightly when installed over a substrate with a higher moisture content. If no allowances have been made for spacing of joints there can be enough movement to cause the underlayment to buckle, pulling the fastener loose. This is especially true when improper fasteners are used or the correct fastening pattern is not followed. Once the moisture content lowers, the wood will shrink resulting in a loose panel free to move up and down on the shank of the fastener.
2) Improper fastening technique – Power nailing has become increasingly more popular with “fast track” building techniques. The problem is that when using a pneumatic nailer it is impossible to tell when a nail has barely missed the edge of the joist allowing the shank of the nail to rub the edge of the joist.
3) Lack of OR improper blocking – The blocking of joists is normally done prior to installation of the subfloor. The norm is to nail the blocking from the top then after the structure is enclosed, the bottom of the the blocking is securely fastened. In more and more cases the blocking is either not done or is not secured on the bottom. This allows the floor joist, when subjected to a bearing load, to rotate or slide rather than transferring the load to the other joist.
4) Improper fastening of interior wall partitions – Is there is a squeak near an interior wall partition, the squeak may be a result of the wall plate being anchored to the subfloor rather than to the floor joist. Occasionally the practice of carpenters is to nail the lower plate into the subfloor which, when walked on, will deflect slightly allowing the subfloor to move, rubbing on the shank of the nail.
5) Improper nails – The use of fasteners that are not designed for flooring purposes such as smooth shanked or coated nails are a major cause of squeaks. When lumber dries there is shrinkage, which is not limited to just the outside dimensions of the lumber. There is direct correlation to the shrinkage and the hold of the nail.
6) Unevenness of joists – With the use of lower grades of dimensional lumber, high yield growth lumber and higher moisture content in lumber we are seeing much more movement to the floor joists. This movement is a result of the lumber drying to its in service moisture content and will result in the lumber shrinking, twisting and bowing. When floor joists are installed they are supposed to be “crowned” upward. If the joists are not “crowned” or are placed randomly, the subfloor will be forced to bridge the high and low joists creating gaps between the subfloor and the low joists, generating a squeak between the movement of the subfloor and the low joist.
7) Ductwork – Structures with forced-air heating systems usually have the ductwork running between the joists and come up through the floor where the discharge vent is located. Squeaks occur when the discharge vent is cut too tight to the ductwork, allowing the deflection of the substrate to rub on the metal ductwork.
The above is an attempt to understand the causes of squeaks and to help prevent them from occurring. All squeaks can be eliminated. It is a matter of determining the source of the squeak and then taking corrective action to eliminate the cause. While this sounds simple, it may not be as sometimes the elimination of an annoying squeak is a major undertaking.