Whether you’re building, remodeling, or purchasing a home, certain flaws are acceptable, while others are deal-breakers. A sloped floor is a situation that falls in a bit of a gray area because it can be barely noticeable or it can cause actual problems. If you find yourself on uneven footing, you may wonder how much floor slope is too much.

Floor slope is not uncommon, especially in homes more than 15 years old. According to the National Association of Home Builders (NAHB), floor slopes less than ½ inch (1.27 cm) over a distance of 20 feet (6.10 meters) are acceptable. Other experts say that anything under 1.5 inches (3.8 cm) is okay.

In this article, I’ll explain how to tell if your floor has a significant slope. I’ll also discuss causes of a sloped floor, when you should be concerned, and some potential solutions.

Measuring a Floor’s Slope

Sometimes, it’s not clear if the floor is actually sloped or whether it’s sagging or just uneven. These are all different but related issues. Here are some ways to measure floor slope and get a better idea of how extensive the problem may be:

  • Use a marble or golf ball. You can place a round object like a golf ball or marble on the floor to see if it rolls away. This will also tell you the direction of the slope and how large the sloped area is. However, this won’t give you an exact measurement, and you may not be able to do this on certain floor types like carpet.
  • Use a level. You can purchase a standard level at any home improvement or hardware store, and they come in various lengths. For determining a floor slope, a longer level is better. 
  • Use a laser level. These tools will use a laser beam to determine the slope more accurately than trying to read it yourself, and you can also use it around your house for mounting items on the wall without having to eyeball whether they’re straight. An easy-to-use basic model is all you need, like this Tavool 50 ft. (15 m) laser level.

What Causes Sloping in Floors?

Sloping in floors is often due to the home’s foundation settling over time, causing the subfloor to become uneven. Wood floor joists can also bend and wear over time.  Older houses commonly have at least some areas of sloping in the floors.

When the issue is due to deflection in the floor joists, building codes typically require the bend to be less than the total length of the joist divided by 360. If the floor is sagging in some places, then this probably indicates joist problems. 

Sometimes, the cause for a sloped floor can be as simple as poorly installed flooring. If flooring was laid on an uneven surface, the result would be uneven or slanted.

Similarly, it’s possible that the concrete slab wasn’t leveled before the flooring was installed, or even if the foundation itself wasn’t leveled well enough.

When Should You Worry About a Sloped Floor?

If you suspect that foundation problems are the culprit for your sloped floor, it’s a good idea to have an inspection completed by a professional. In the meantime, look for other signs of foundation problems like cracks in the walls, around doors and windows, or in the visible exterior foundation.

Consider the age of your home when you’re determining if a sloped floor is a cause for concern. If you notice a sloped floor in a recently built house (say, within the last 5-10 years), it may be a sign of bigger problems.  

Ceramic wall tiles can be good indicators of recent shifting due to foundation settling. If you notice cracks in newly installed wall tiles, it could be a sign of recent movement.

Can You Repair a Sloped Floor?

You can repair a sloped floor by having foundation work done, but this can get expensive. Another option is to level the floors on top of the foundation. This is much simpler and only involves installing new subflooring. If floor joists are the issue, these can be repaired by a professional.

If the floor slope is bothersome, there are options to resolve the issue. However, if you’re fine with it, it isn’t necessarily something that needs to be repaired. As I mentioned, this is often part of the normal settling process that occurs with older homes.

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