How Much Floor Slope Is Acceptable?

If the floors in your home are not level, then you have a floor slope. In many cases, a sloping floor is the natural consequence of an aging home, but sometimes floor slopes reflect bigger problems in a home’s foundation.

According to the NAHB, the acceptable amount of floor slope is ½ inch in 20 feet. Individual contractors differ in opinion on how much floor slope is acceptable. The best solution is to hire a trained professional to inspect the floor slope to determine whether it is a sign of a structural problem.

There are many potential reasons for sloping floors, with some concerning the integrity of a home’s foundation. Sloping floors is an important issue to address early on since this could happen because of drainage issues or cracks in the foundation. Keep reading to learn more about how much floor slope is acceptable and what you can do to fix sloping floors.

How Much Floor Slope Is Acceptable?

Depending on the organization or contractor you speak to, the acceptable amount of floor slope can range from half-inch to one inch in 20 feet. A floor slope that is higher than one inch is a cause for concern by most standards, including the half-inch in 20 feet standard in the National Association of Home Builders (NAHB) performance guidelines.

Aside from relying on measurements, you can also defer to your own judgment to determine the acceptable amount of floor slope. If you notice that you are regularly tripping on your floors or that objects on shelves are falling frequently, then clearly there is too much floor slope.

What Causes Sloping Floors?

There are three primary reasons for sloping floors, which can cause more or less damage to the integrity of your home depending on their severity:

  • House settling
  • Damaged floor joists
  • Foundation damage

House settling is a minor concern when compared to damages to the foundation or sagging floor joists, as this is commonly seen in aging houses where the house sinks deeper into the ground. Damages to the foundation and sagging floor joists are structural issues that can cost thousands of dollars to fix if ignored for too long.

Sloping Floors from House Settling

Since house settling involves the shifting of a home’s foundation, house settling can lead to sloping floors. House settling is a phenomenon typically seen in aging houses. The process of house settling involves the gradual submergence of a house deeper into the ground because of the weight and force exerted by the building over time.

Some common symptoms of house settling include:

  • Sloping floors
  • Small cracks in the foundation, ceiling, or walls
  • Gaps between windows and walls
  • Damaged water pipes
  • Difficulty opening windows and doors

These symptoms arise from the misalignment of the home with the original framing put in place. Or in other words, the doors, windows, walls, and ceiling gradually become slanted and displaced into odd angles that make a house’s architecture function less properly. Sloping floors is one of the easier symptoms to notice when inspecting your home since floors are usually in constant use.

In the beginning, the symptoms of house settling will probably not be noticeable to you, but over time these symptoms may become more and more pronounced. The best way to manage house settling is to inspect your home every few months for foundation damage, especially damage involving moisture and leakage around your foundation.

Sloping Floors from Damaged Floor Joists

The parallel pieces of wood that maintain the integrity of your flooring are floor joists, so when your joists are damaged this can lead to sloping floors. Healthy floor joists are crucial for maintaining sturdy and reliable flooring in your home. However, you may encounter issues with floor joists if there are weak joists underneath your floor suffering from too much moisture that can cause wood rot.

Aside from wood rot, alternative causes for damaged floor joists are identical to those of sloping floors, such as framing issues or structural problems with the foundation.

A common problem is sagging floor joists that produce areas where the floor is sloped on all sides. These areas are called sagging flooring. Sloping floors and sagging floors slightly differ regarding how they manifest in your home, but both reflect the same structural problems relating back to damaged floor joists, framing issues, and foundation damage.

Sloping Floors from Foundation Damage

Sloping floors can result from structural damage to your home’s foundation. A foundation is the essential, weight-bearing structure that keeps the architecture of your home stable. When the foundation is too damaged, this can result in catastrophic consequences for your home along with sloped flooring.

Foundation damage causes sloped flooring because of the following issues:

  • Stability problems related to the soil underneath the home
  • House settling
  • Unchecked drainage issues that lead to water damage to the wooden joists supporting the flooring

As you can probably tell, these issues with the sloped flooring and foundation damage are interconnected, so when you ignore one issue you are likely ignoring an entire collection of issues in your home. Foundation damage is one of the major causes of sloped flooring, while sloped flooring is a symptom of foundation damage.

How to Fix Sloping Floors

Sloping floors are a symptom of structural problems within the home. Unless the structural problems are addressed directly, you cannot fix sloping floors and reestablish parallel flooring throughout your home. The best way to accomplish this is by hiring a trained contractor to come into your home for a thorough inspection.

During the inspection process, a contractor will spot damaged areas and measure the severity of the damage using thermal image technology and other devices. Contractors will look for drainage and leakage problems, cracks in the walls and ceiling, damage to the foundation, and more.

At the end of the inspection, the contractor will advise you on different actions you can take to mitigate the problems in your home to effectively deal with sloping floors and other issues. If your home has deep cracks in the foundation or huge leak problems, then costs will run much higher. Conversely, small cracks in the foundation or minor leakage or drainage issues are much cheaper to fix.

How to Prevent Sloping Floors

Ultimately, the best way to fix and prevent floor slopes is to address minor issues in the framing or foundation of your home before they become worse. By inspecting your home every few months, you can catch most problems that cause sloping floors early long before you need to worry about paying high prices for contractors or engineers to make repairs to your home.

Here are some questions you should ask yourself when inspecting your home:

  • Is the floor sloped and, if so, how severe is the slope?
  • Are there cracks on the wall, ceiling, or foundation?
  • Are doors and windows difficult to open?
  • Is the slope of the floor relatively the same across time or is it getting worse?
  • How old is the house?

By going through each of these questions, you will find the answers you are looking for regarding sloping floors and whether this is a symptom of a more serious problem that needs to be addressed.


Most professionals will tell you that the acceptable amount of floor slope ranges from a half-inch to one inch in 20 feet. The most recent edition of the NAHB performance guidelines specifies that one-half inch of floor slope in 20 feet is acceptable.

There are many causes for sloping floors such as house settling, foundation damage, and weak floor joists. The most effective way to deal with sloping floors is to regularly inspect your home every few months to prevent large-scale problems in your home from developing.

If sloping floors are too much of a safety hazard in your home or you suspect they are a symptom of a larger problem, then hire an experienced contractor to inspect your home.