how much floor slope is acceptable
Kristina Davis

How much floor slope is acceptable? This must be a cause of concern for you.

Slopes and other irregular floor levels have been a constant issue for most homeowners. Although most don’t see much of an issue with the slopes. 

Buildings are bound to develop slopes, either with aging, poor installation, or a fault in the structure of the house.

Some of these slopes aren’t much of a concern as it might just be a cosmetic issue with the building.

While others are quite serious and a threat and hence require immediate inspection and a lasting solution.

This article shall be discussing everything we need to know about slopes. From how much floor slope is acceptable, how to detect one, to how you can fix an irregular one.

So read along to know if that slope is one to be bothered about.

The National Association of Home Builders(NAHB), approved floor slopes less than ½ inch over a distance of 20 feet. Although this is widely accepted, there are some contractors and builders with different opinions.

Sloping or Sagging?

sloping or sagging floor

Sloping and sagging, although they are two similar flooring issues, are quite different.

It is important for us to know and be able to identify each of these two flooring defects.

Sloping is a flooring defect that occurs as an uneven effect towards one side of the floor. More like a little slide.

On the other hand, sagging occurs when the floor is uneven on all sides. More like a little pit on the floor.

Another thing to note is that both sloping and sagging can be caused by similar causes.

Sagging is a defect that requires more concern as it signifies a more structural problem than sloping.

Note: Sloping and sagging are two different things

How To Identify Floor Slope

identify floor slope

Identifying slopes in our home is quite easy. It requires no technicalities.

We can notice it in our everyday observation of our home.

Here are a few methods for determining floor slope.

  •  We can feel the slope on the ground with our feet when walking. We tend to notice this first.
  • Through books and items falling off the shelf and stands of our home due to imbalance of the ground. 
  • Also doesn’t happen as often but through water puddles on the floor. In case there is a water spillage on the floor.
  • Window and door misalignment could be a cause of floor sloping

Causes of Floor Slope?

floor slope causes

There are just a few causes for floor sloping, some are cosmetic defects while others are majorly a structural effect.

Below are some of the causes of floor slope:

Building Foundation Settling

As the building ages, the foundation is very much likely to settle. Settling involves the sinking of a building foundation.

Settling mostly occurs in older houses but can happen in new houses with foundations built on expansive soil.

Poorly Installed Flooring

poor flooring

If the subfloor of a home isn’t done properly or there is an issue on the main floor of a home. Then there is a high tendency for the floor to develop slopes.

While this can be fully avoided, it is an unintentional mistake by the builder or floor installer. 

Damaged Floor Joist

This too causes sloping of floors. Floor joists are parallel pieces of wood that serve as support beams and run vertically to the ceiling joist.

A joist is put underneath the flooring of a building to give support to the floor.

They can become damaged or faulty either due to time or water leakage.

Note: This weakness of the joist causes the floor to be slopy.

Foundation and Framing Issue

issue in foundation and frames

A building foundation, if not built properly, could shift and cause the floor to slope.

This is probably the worst cause for sloping. A sloping like this might only continue to get worse. 

This mostly happens when unprofessional builders make mistakes in the foundation of the house. Or the foundation is done on poor and expansive soil. 

A similar occurrence might happen when there is water leakage just beneath the house, that continually affects the foundation.

This can also cause the foundation and frame of the house to develop issues.

How To Measure Floor Slope

measuring floor slope

Knowing how to measure a floor slope might sound like unnecessary knowledge.

But if you are worried about the slope in your home it is important for you to know how to measure a slope. 

Measuring a slope is actually quite easy. We have three main ways of measuring a floor slope:

Use A Golf Ball Or A Marble

This is a very simple technique for measuring a slope. All you have to do is place a marble or a golf ball on the suspected area of the ground.

If there are slopes on the floor, the ball would roll in the direction of the slope. 

Also depending on the speed, you can tell how steep the slope is.

Tip: If it remains still, then possible there are no slopes.

Use A Level

use level tool on floor

A level is an instrument used majorly by builders to check the smoothness or steepness of a surface.

Placing the level on any surface, you can measure the steepness of the slope. 

A good rule of thumb is to purchase a longer level such as a 6foot level.

As this will give you a more accurate measurement and you can measure long distances.

Laser Level

A laser level uses a more advanced way of checking slopes. This instrument employs laser beams for checking the steepness of a slope. 

You can get this instrument at big stores.

This is a very handy tool as it is easier to measure a slope and can aid in other activities that involve calculating surfaces.

How Much Floor Slope Is Acceptable

The question of what is acceptable floor slope has bagged a lot of debate and opinions.

The widely accepted measurement which was given by the National Association of Home Builders is less than ½ inch over a distance of 20 feet.

Although numerous building contractors give their own measurements ranging from below  ½ inch to 1.5 inch.

Anything above 1.5 inches to 3 inches shover a distance of 20 feet is a cause for concern. 

Should I Be Concerned About Floor Slope?

floor slope concern

A major concern among certain homeowners is how much floor slope is too much in my home.

As stated above, if the cause of the slope is a cosmetic issue, then there is really no need to be worried.

But if it is a foundation problem then you should probably the concerned.

Typically old houses are bound to develop slopes either due to weak foundation or ground change.

In case you notice a slope in a new house between 5-10 years old, and a slope that is progressively getting worse, then you need to take action and confirm if it’s a foundation problem.

Signs That Floor Slope Is A Major Concern

floor slope major concern

Below are some signs to check for to know if your slope is caused by a structural defect:

  • Wall cracks
  • Difficulty in opening doors and windows
  • Crack in ceramic wall tiles
  • Crack in any visible exterior of foundation or concrete slab
  • Ceiling cracks
  • Soil Creep
  • Number of sloped areas
  • Presence of Sagging
Tip: When you notice sloping, always contact an expert to help evaluate it.

Methods Of Fixing Floor Slope

fix floor slopes

The best-known method for fixing a floor slope is to determine the problem and the cause on time.

If the floor slope is a minor problem and not a foundation issue, you can either decide to live with the slope. 

So long as you are okay with it.

But if you are not, you can level the floor, either by getting a new subfloor installed or by patching the affected area. 

If the slope is caused by joists, then it is best to seek the help of a professional to fix the joists issue. 

Also if the slope is caused by a foundation or structural defect. It is also very important to seek the help of a professional as soon as possible. 

The professionals are structural or geotechnical engineers or any other qualified individual.

They would inspect the slope and signs to know if it’s a structural problem before proposing a solution. 

Although this might be expensive it is best to hire a pro and figure out a solution.

Foundation problems can lead to more problems than sloping.


Ultimately, how much floor slope is acceptable entirely depends on you as a homeowner.

So long as the slope isn’t a foundation or structural cause. You can decide to live with it or level it up. 

An extra tip is to ensure to inspect your house frequently, at least twice a year.

This way, you don’t get caught unaware, you notice sloping and sagging floors. And can detect if it’s a foundation problem or not. 

I hope this article has been helpful, and I hope you learned a great deal about sloping floors and how to detect them.

Thank you for reading, see you again next time.