Are Sagging Floors Dangerous?

You’re casually ‘chilling’ at home watching TV until you notice a part of the floor that looks like a little pothole. You walk into it and notice the creaking and instability around that area. What you’ve just seen is a sagging floor. Given its connection to the house’s foundation, it’s likely you freaked out at first. Is the house collapsing? Is the floor going to sink one day? You probably have these thoughts running through your head.

At this point, you definitely want to know how dangerous these sagging floors are. Are those wild thoughts in your head unfounded or actually true? Well, you’re about to find out.

Are Sagging Floors Dangerous

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What Causes Sagging Floors?

Knowing about the various causes of a sagging floor gives you a good impression of just how dangerous it could be. Also, you have a rough impression of how much the fixing could cost. While the causes tend to vary, here are a few of the more common reasons:

1. Weakened Joists

Let’s take you through a few construction basics. After building a house, after laying the foundation (using a concrete slab or the ground), the concrete columns are erected. Then, the next step is to add wooden joists that help hold up your subfloor. Then, they lay the flooring you see in your living space on top of the subflooring. Now, these joists are wooden and are made out of wood types such as spruce, western red cedar, hemlock, etc. Common to all types of wood are softening and rot if exposed to moisture.

Floor Joist
Joists. Credit: BUILD.

Once there’s a continuous supply of moisture to the joists, they start to soften and cannot handle the weight of the house anymore. This leads to sagging of the floors. Sometimes, the weakening of the joist could be due to the aging of the wood.

2. Damp Crawl Space

The crawl space is the space between the concrete slab or foundation and the subfloor. The joist is what connects the former and the latter. If the crawl space is damp (which means there’s a water source), it could cause the joists to get damp or attract insects. You now know the effect of the former. For the latter, these insects (termites) could start eating into the wooden joist and damage, hence making the floor start sagging.

3. Shifting or Eroding Soil

This also has to do with the joist. However, in this case, the soil around your joist keeps giving way, hence, leading to the joists losing their soil support. This way, the joist start to lose their structural integrity leading to your floor sagging.

How Dangerous are Sagging Floors?

In most cases, a sagging floor doesn’t have detrimental effects on the house’s inhabitants. Unless you have a senior or little baby in the house, it’s quite unlikely that anyone will get injured walking on the spot. In fact, many people do live with sagging floors in their house (if it’s not too bad). However, if you plan to get your insurance company to fix it, you should get it checked as soon as possible. This is because the insurance company will not cover the repair if you allow the damage to get worse.

Still, on the topic of danger, sagging floors pose a larger threat to your pocket. This applies to people who want to sell their house or when you want to repair it. With a sagging floor, the value of the house could drop by as high as 20%. Also, realtors have an obligation to inform potential buyers of your house about the sagging floor; hence, it’s not a detail you can leave out. About the repair, fixing a sagging floor could cost anywhere between $1,000 and $10,000.

A sagging floor is more of an indication of a structural defect occurring at the base of the house. Some other symptoms which accompany a sagging floor include cracks on the interior walls, tight or loose windows and doors, etc. If the sagging floor is quite steep, you might want to get a professional to inspect the floor. This could mean the structural support beneath your subflooring is almost about to collapse. In this case, you need immediate intervention. 

However, you might be wondering, “What level of steepness can be considered to be too steep?” According to building codes, one-eighth one-quarter steep in 20 feet is considered normal. However, if the steepness extends to one-half or one inch in 20 feet, then you should take it more seriously. If it ranges close to 3 feet, then your floor needs immediate intervention.

How To Fix Sagging Floors

While a sagging floor isn’t a housing problem you should try to fix yourself; knowing how the professionals fix it would help you understand the fee they charge you. Below are a few ways that professionals use in fixing sagging floors:

1. Encapsulation

This involves covering the floors, walls, and ceiling of the crawling space of your house with thick polyethylene plastic. This will help prevent the entry of water and keep the crawl space dry. This ensures the joists do not become weakened easily. Apart from this, it also offers other benefits such as:

  • Provides extra space for storage
  • Ensures better heat circulation, hence reducing ventilation costs.
  • Prevent the growth of mold.
Crawl Space Encapsulation. Credit: Restoration King

2. Joist Sistering

Instead of removing the joist completely, which would cost more and lead to more work, they could use a process known as joint sistering. This involves adding a similar piece of wood to the joists to support it. Also, they could use a push pier instead of the extra wooden support. Push piers are steel pipes that are installed into the foundation. These will offer even stronger support to the subflooring than the joists.

3. Proper Drainage System

In most cases, water only finds its way to the crawl space because of the poor drainage system in the home. If your crawl space has regular exposure to water, you should endeavor to get a professional to rectify the drainage system. They will help create a drainage pipe to divert water away from the crawl space, keeping the crawl space and the joists dry. This will also prevent the invasion of insects which could destroy your joists.


While a sagging floor could cause problems with the aesthetics of your house, it doesn’t have to be necessarily life-threatening. However, do not just assume you can live with it because it doesn’t look dangerous. It is better to get the professionals to consider the damage before deciding on the best step of action.

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