Floors and Structure

There are two different questions that I usually get during a home inspection regarding floors. The first question, why are the floors squeaky. The second question is how come I notice a slight bounce in the floor when I walk on it. Both questions are asked by the buyer because of fear of structural problems. Usually neither of these situations is due to structural problems associated with the construction of the house. In fact, building codes do allow for floor deflection and some bounce in the floor. The question then becomes to what degree the floors are deflecting. I will start by discussing squeaky floors first and then finish with the question of floor deflection.

If you are noticing squeaky floors in your home or a home that you are going to purchase the good news is that squeaky floors are not a structural problem. A floor usually squeaks when the flooring finish or sub-floor is not tightly attached to the joists below. The sub-floor must be securely tightened to the joists and the floor finish must be adhered tightly to the sub-floor. When the flooring is not tightly secured, it sits just off the support in some spots. When someone steps on the flooring in this area, it is pushed down onto its support. When the foot is taken off the floor, it springs back up. This rubbing of flooring components and it fasteners causes the squeak. Solving the squeaky floor problem may take some investigation. The squeak depends on the floor finish, the sub-flooring used, and type of fasteners used. For instance a hard wood floor may squeak due to nails sliding up and down while a carpeted floor may squeak due to poor sub-floor attachment. If the noise is isolated and not excessive most home owners will usually wait until they change floors to fix the condition. If the squeaking is excessive you may need a professional to further examine and take apart the floor to get at the root cause. Remember, the solutions may be different based on your final goal. If you have an old house and want to keep the truly amazing older wood floor, then your solution will be different than a client who has an outdated floor that he was looking to change anyway.

The deflection of a floor and joist system in modern construction may be quite surprising. Many codes allow a floor to deflect 1/360th of its length under normal live loading. This equates to a ½ inch floor drop for a span of 15 feet. A ½ inch drop over the distance of 7 ½ feet is certainly noticeable. The above holds true for live loading, which is the weight of the people and furniture in the structure, therefore the same structure without any furniture will not have a noticeable deflection until you furnish the house. While this is permitted by many building codes, it may not be satisfactory for you. Building codes are intended to be minimum standards. For this reason many home builders will go above and beyond the building codes. For instance, a very brittle floor finishing material, such as ceramic tile, would not tolerate a flex as above. More rigid floor structures are required where the flooring is brittle. Furthermore, making the sub-floor more rigid by adding cement or additional sub-flooring will create an additional load on the joists which must be considered.

The bouncy floor may be fixed in a number of ways. It really depends on the access that you have to the floor underneath. You may be able to make a floor more rigid by adding cross bracing or screwing plywood to the bottom of the joists. Also, adding a support beam will also solve the problem. Of course the solutions depend on the amount of deflection you have and the budget you are working with. If you are living in the house over the long term you may want to consider an option that will allow you other flooring options down the road. As always, seek the advice of professionals before you start your project.