Floor Joist Cross Bracing

A frame constructed with floor joists for a home.

Whether your home is new or old, it is sometimes necessary to install floor joist bracing in order to eliminate squeaking and deflection in the flooring itself. Bracing will stiffen a floor system, prevent floor joists from twisting, and increase overall stability. However, there are actually two types of floor joist bracing commonly used: cross bracing and solid blocking.

Cross Bracing

Cross bracing, sometimes referred to as bridging, is the most common type of flooring reinforcement. While it does not offer as much support or prevent joist flexing as well as solid blocking does, cross bracing does have some definite benefits. Cross braces are easier to install than solid blocking, but the main benefit of this technique is that it allows for easy access to electrical and plumbing elements, making future repairs of those systems simpler to accomplish.

Cross braces are typically constructed from wooden 1x4s, although metal cross bracing ties are sometimes used as well. Cross braces may be installed during the construction process or added to older homes, and it involves nailing small wooden braces from the top of one floor joist to the bottom of the next joist, and vice versa, to form an X. Working your way across the floor, add the braces between adjacent joists, one at a time, at eight-foot intervals.

Solid Blocking

Providing more support and rigidity than cross bracing, solid blocking is a reasonable alternative but can be an obstacle for running plumbing pipes and electrical wire between floor joists. Solid blocking should be used where floor joists overlap over beams. It should be placed at eight-foot intervals between any floor joists 2x10 or longer.

Floor Squeaks

Most floor squeaks occur because either the subfloor or finished floor is loose. This can cause it to rub against a popped nail. If this is the case, no amount of bracing will correct the squeak. Instead, the floor must be nailed or screwed down directly to the floor joists to eliminate the sound. The utilization of cross braces, however, will commonly reduce squeaking to a certain degree and will provide stability for any floor, making it worth the effort and expense whether it eliminates squeaking or not.

If neither cross bracing nor nailing floors directly to floor joists is effective in stopping a floor from squeaking, then the joists may require shimming. Placing a shim on top of the floor joists directly under the flooring is fast, easy, and often effective. Be certain to push the shims in tightly, but take care not to pound them in hard enough to push up on the floor from below.

Special Considerations

Although bracing a floor is not difficult, here are a few things to keep in mind. It is crucial not to split the ends of wooden cross braces when nailing them onto floor joists. Splitting the ends is a common mistake that will weaken the bracing and lower the integrity of the flooring system.

Braces should also be installed prior to the installation of floor sheathing, also referred to as subflooring. This will ensure proper joist spacing and assist in the ease of sheathing installation. Because some cross braces are made from treated lumber, which is corrosive, be certain to use corrosion-resistant or stainless steel nails and fasteners. When using metal cross braces for the floor joists, be sure that they have been coated in an anti-corrosive material.