Sloping, Sagging, or Settled Floors

Sloping, sagging, or sunken floors can be common problems observed in older properties. As a seasoned home inspector with extensive experience examining thousands of houses, I have encountered various degrees of floor movement, regardless of the age of the dwelling.

There are three primary causes behind these floor irregularities, which we will discuss below.

When floors slope toward the center of a home, it often indicates “settlement” or movement of the floor structure’s supports. These supports, which may consist of brick or CMU block piers, steel columns, or wood posts, must rest on properly installed, adequately sized concrete footings to bear the weight of the structure. Typically, these supports bear over 60% of the home’s weight, which can range from 300,000 to 400,000 lbs for an average-sized house. Unfortunately, if the supports or footings are undersized, they are likely to “sink” under the immense weight, causing the center of the home to sag to some degree. This is an unavoidable consequence, as every action has an equal and opposite reaction.

In cases where floors slope toward the perimeter walls, it is highly probable that the foundation walls and/or their related footings have experienced movement or settlement. These walls carry the remaining 40% of the structure’s weight, amounting to at least 120,000 lbs.

Lastly, there are instances of “wavy” floors, where the floor height starts at a “normal” level at the perimeter of the structure, but sags between the perimeter and the center, where the main beam or girder lies beneath. This can be attributed to factors such as the spacing and size of the floor joists, as well as the effects of age and moisture on their integrity. There is a code-based formula to determine the allowable deflection (sag) for a joist in its span, expressed as L/360. By dividing the span of the joist in inches by 360, you can calculate the maximum acceptable deflection. For example, if a joist spans 10 feet, dividing 120 by 360 results in approximately 5/16″ of allowable sag in 10 feet.

What are the Repercussions of Sloping Floors?

Throughout my extensive inspection career encompassing nearly 3000 assessments, I have never encountered a floor that has “failed” or collapsed solely due to sagging or sloping. However, it is important to note that this possibility cannot be entirely ruled out. The primary concern with floor movement is whether it has come to a halt. Unfortunately, no one can determine this during a single site visit, but rather the floors, foundation walls, and/or floor structure supports would need to be monitored over a period of time, looking for continual movement. You certainly wouldn’t want to find yourself constantly scrutinizing your floors for signs of further instability, and if it occurs it’s you on the hook for the repair costs.

What are my options?

While minor deviations of floor movement of 1/4″ or even up to 1/2″ to 3/4″ can be attributed to construction variations, anything beyond this range should raise concerns and prompt consideration of stabilization measures. Stabilization involves repairs performed by a foundation contractor to prevent further settling of the floors. Keep in mind that these repairs are often costly, and it is prudent to factor them into your decision when purchasing a home. It is important to remember that someday you may want to sell the property, and potential buyers might insist on having the floors stabilized if the issue has not been addressed beforehand.