Are Sagging Floors in a Old House Dangerous?

Only 30 percent of homes in America have basements. Most of the remaining 70 percent have crawl spaces or are built directly on concrete slabs. 

While every type of foundation has its pros and cons, homes with crawl spaces are among the most likely to suffer sagging. But what do sagging floors in an old house mean? How serious are they?

Keep reading now to get the facts.

Why Floors Sag

Most homeowners don’t spend a lot of time thinking about what lies beneath the hardwood or carpet of their home’s floors. But when flooring issues arise, this little-considered aspect of the home becomes a critical question. 

Floor Construction Essentials

When constructing a house, builders may first lay down a concrete pad or may choose to build directly on the ground. In either case, the first layer of wooden construction is floor joists.

Joists are long lengths of wood set down at regular intervals. Common choices include 2×10 or 2×12 boards set at 16- or 24-inch intervals across the foundation. Joists are typically made of sturdy woods such as:

  • Hemlock
  • Douglas fir
  • Southern yellow pine
  • Spruce
  • Redwood
  • Western red cedar
  • Eastern white pine

The exact combination of wood type, length, and span depends on a variety of factors unique to each house. Once joists are in place, builders lay down a subfloor and then place the interior flooring that you see in your home on top of that. Once enclosed, joists are accessible only through your crawl space or removal of your entire floor and subfloor. 


Over time, joists can deteriorate. Exposure to moisture or standing water can cause joists to weaken and rot. When this happens, they can no longer hold the load of interior home flooring.

Alternatively, when joists are laid on the ground instead of concrete, the ground around and underneath them can begin to shift or erode. This, too, can weaken or damage joists.

In either case, the result is often a sagging floor. Other signs of damaged joists and impending sag include:

  • Buckling, crumbling, or cracks in your foundation
  • Cracks forming in the interior of a home, especially around walls and corners
  • Windows and doors that become either very loose or very tight in their frames

Are Sagging Floors Dangerous?

Sagging floors are a sign of serious damage to the joists beneath your home and the structure of your home overall. Left untended, this can lead to injury, property loss, and disaster. Worse, insurance companies often will not pay for such losses or repairs if you ignored the issue once the early signs became visible. 

It is essential that homeowners make fixing sagging floors a priority as soon as they recognize there is a problem.

Can You Fix Floors in a DIY Project?

Some websites may suggest that it is possible to jack up and repair your floors yourself. Attempting to do so, however, is extremely dangerous and unwise. 

In addition to risking severe injury during the process, homeowners:

  • Risk further injury and expensive damage to their home and property if the job isn’t done correctly
  • May compromise their homeowners’ insurance coverage if the job isn’t done correctly
  • May be unable to sell their homes in the future if the repairs do not meet local code
  • May find that they must repeatedly fix the problem at great expense if the first fix is not enough

This last point is particularly relevant. This is because most joists fail due to exposure to water in the crawlspace. If the fix does not permanently and effectively address the moisture issue, the problem will continue to recur regardless of what other steps homeowners take. 

For all these reasons and more, it is essential that homeowners not attempt to fix a sagging floor crawl space themselves. Instead, they should always hire an experienced floor joist repair contractor to do the job. 

What to Expect

If you notice sagging floors or other signs of potential concern, contact a professional and schedule an inspection right away. After inspecting your home, a professional will be able to tell you:

  • What kind of damage you have and how extensive it is
  • What steps you need to take to correct the damage 
  • Roughly how much replacement joists, framing repair, new flooring, and other project components will cost
  • Whether you need French drains as part of the project

This will set you up with everything you need to know to make the best decisions. 

Interior French Drains

One of the aspects of a project to fixing sagging floors that many homeowners don’t anticipate is the need to install French drains. While French drains can sound intimidating, in practice they are fairly simple. They involve:

  • Cutting a trench in the ground to lead water away from somewhere it should not be (your crawl space) to some more appropriate outlet
  • Lining the trench with gravel and suitable fabric
  • Laying a perforated pipe in the trench to channel water

Done correctly, this combination of pipe, fabric, and gravel directs water away from problem areas. It keeps your crawl space dry and protects your joists, foundation, and home from:


Homeowners should not attempt to install French drains themselves. Even small errors in installation can result in drains not working correctly. That, in turn, can lead to more home damage. 

Most floor joist repair contractors can handle French drain installation as well as joist repair. This gives homeowners a solid, reliable, and fully insured solution to their troubles. 


Another option for homeowners who discover they have moisture problems and joist damage is encapsulation. After joist repairs are complete, a floor joist repair contractor can seal off your crawl space, preventing any new moisture infiltration. They use heavy sheets of polyethylene plastic to cover your crawl space’s:

  • Floor
  • Walls
  • Ceiling


In addition to preventing water damage and dry rot, crawl space encapsulation offers a host of other benefits. It can:

  • Prevent the formation of foundation cracks
  • Stop windows from sweating
  • Prevent pest infestation in your crawl space
  • Reduce home heating and cooling costs 
  • Prevent mold and mildew
  • Improve your home’s air quality
  • Create new storage space by making your crawl space safe and suitable for this purpose


Most importantly, whether you choose French drains or encapsulation or both, addressing the moisture problem in your home will provide lasting peace of mind. 

Sagging Floors and Old House FAQs

Homeowners often have questions about the process of repairing sagging floors. Here are some of the most common questions and their answers.

There is no single method of repair that works best for every home. Variations in home design, location, geography, and other factors can all play a role in determining the best option for your home. An experienced floor joist repair contractor can help you choose the methods that are right for you. 

Nationwide, the average cost to repair sagging floors is around $5,000. Your costs could be notably lower or higher depending on:

  • The size of your home
  • The state of your crawl space
  • What steps you need to take to repair existing damage and prevent future damage

The best way to get a reliable estimate is to contact a local joist repair expert for an inspection.

An experienced joist repair contractor can assess and repair all the various types of damage your home may have sustained. In fact, some treatments, such as encapsulation, are effective against a wide range of potential hazards. This means that selecting the right treatment can give you the biggest possible bang for your buck!

 Sump pumps can be very useful in the right circumstances. They are more likely to pair well with other drainage or moisture control options and treatments than to wholly replace them, however. 

Finding the right combination of options for your home can be tricky. Talk to an experienced contractor about your priorities and concerns. They will be able to assist you in selecting the best treatments and solutions for your property. 

Schedule an Inspection Today

If you have seen any of the tell-tale signs of sagging floors in an old house, don’t wait. Schedule an inspection and let the experts help you identify the best ways to protect your home today.


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