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Sagging Floors Over A Crawl Space

A weak crawl space support post with slight mold and rot damage

Poorly Designed Support Posts

Many crawl space support systems were hastily and cheaply made, and are not what your home needs. In many cases, it's a virtual miracle the structure is still standing at all!

Addressing this problem quickly can prevent potentially serious structural damage to your home.

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Across our network, our experts visit well many thousands of crawl spaces each year. Of the ones we see, we estimate that 83% of them show signs of an existing or developing structural problem.

Of course, we see some of the worst crawl spaces out there. Let's say that only 50% have a problem.

With US Census Reports showing 27,000,000 crawl spaces in the United States, that makes 13.5 million crawl spaces that are in need of structural repair and reinforcement!

Reasons That A Crawl Space Sags

  • Supports That Are Too Few & Are Spaced Too Far Apart
  • Weakened Floor Joists & Girders Due To Moisture, Wood Rot, & Similar Forces
  • Existing Columns That Have Settled Due to Weak Soil

Many of the options available for repairing a damaged crawl space include solutions that temporary and will need constant maintenance to be successful at all.

Other lead to further structural damage as they're installed, and may still be only a temporary solution.

free crawl space structural repair quote

At Basement Systems, we provide permanent structural repair solutions for homeowners interested in repairing their sagging or sinking crawl space.

Our heavy duty SmartJack™ Crawl Space Support System is designed with long-lasting, durable galvanized steel -- and an award-winning design! We'd like to meet with you to explain how our warranted system can work for you! Contact us by phone or e-mail today to schedule a free, no-obligation crawl space repair quote!

A rotting crawl space floor joist

Crawl Space Mold & Rot

Mold and rot will grow on the structural wood of a crawl space when a wet, humid environment is present.

This is especially true when the wet fiberglass is present between the joists, as it holds moisture against the wood surfaces.

More about Crawl Space Mold

Sagging Crawl Space Damage

If you suspect that there's a structural issue with your crawl space, it's important to address the problem right away.

As a crawl space sags, it begins to pull down everything above it. One of the early signs of a weakened structure will be a "springy" floor above. Soon afterwards, the floor will show signs of sinking downwards.

As the floor sinks around doors, their operation can become affected. Doors may stick or jam shut, and the door frame can become skewed.

A sinking crawl space will also pull anything nailed to it downwards -- including the framing of your walls. This can lead to cracks forming in your drywall surfaces, which can be very alarming!

Odors Accompanying A Sagging Structure

In many cases, a crawl space is sinking due to mold and rot in the floor boards. As the mold builds up, it can lead to odors and allergens in your living space. The effects of this should not be underestimated!

More about Crawl Space Mold & Your Health

Options For Crawl Space Structural Repair

When it comes to repairing a crawl space, there are great options, good options, and options that probably shouldn't be tried at all. The same rings true with most home repairs, in fact.

Since you have so much depending on your crawl space to remain structurally sound (the entire house), it's worth the time to look into the options for repair. Some will provide permanent, warranted solutions, while others may do more damage than good -- literally.

A breakdown of the common ways to repair a sagging crawl space follows:

Wood shimming on a crawl space support post

Additional Shimming

Before additional shimming is installed, the floor must be mechanically lifted upwards above its original position -- so that the shimming can be placed and the floor lowered back over the support.

Once the lift has taken place, pieces of metal or wood can be inserted into the gaps at the top. The structure is then lowered back on the supports.

Since the floor is "overlifted", the process can lead to additional structural damage as it's conducted.

It's also important to remember that if the crawl space supports continue to sink afterwards, the process will need to be repeated.


concrete masonry unit columns installed in a crawl space

Concrete Masonry Unit (CMU) Columns

CMU Columns are made with concrete blocks, which use shimming along the top to fill in the gaps. These are very common in crawl space construction.

If your crawl space has too few CMU columns installed, additional columns may be added to enhance the support system. Each one will need shimming as part of the installation, and overlifting of the structure will be necessary.

Typically, CMU Columns will need at least three visits, separated by several days apiece, to install. This gives time for the concrete footings and block mortar to cure. If these support columns also sink, then additional shimming will be needed to repair them.


an installation of light-duty crawl space support jacks

Light-Duty Jack Posts

Often, a contractor will opt to install light-duty jack posts in the crawl space to restore structural support.

These posts span the distance between the floor and the structural wood (joists and girders), and can be adjusted so that overlifting is not necessary.

However, light-duty jacks have a low load-bearing capacity (typically 15,000-18,000 pounds), and many will be needed to achieve the proper support.

These support posts are narrow at the bottom, and can sink easily into poor supporting soils. However, their steel design is very vulnerable to corrosion, and can be difficult or impossible to adjust when they need to.


two SmartJack® crawl space support posts installed

SmartJack™ Crawl Space Jack Posts

The SmartJack® Crawl Space Support System is heavy duty jack post system that's warranted for long-lasting strength and adjustability in your crawl space.

Installation is very similar to light-duty jack posts, except that a special base is created underneath each post, distributing the weight borne by the posts and virtually eliminating the risk of sinking supports.

A galvanized steel design resists corrosion, while these powerful posts are capable of supporting bearing loads of 60,000 pounds or more. Installation is often completed in a day or less. In many cases, the jacks can be adjusted to lift the floor back up -- with no additional damage to your structure!

We Can End Your Crawl Space Moisture Problems!

At Basement Systems, our network of crawl space specialists can provide you with a permanent solution for your sagging, structurally weakened crawl space. We pride ourselves on our fast, professional installations, as well as our written transferable warranty.

To sign up for a free crawl space structural repair quote with your local dealer, contact us by phone or e-mail today! Each free quote includes an on-site inspection, a professional consultation, a full-color copy of our crawl space book, and a customized, written cost estimate!

We serve throughout North America and Europe, including Canada and the United States. We look forward to hearing from you!

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Quality, Innovation, Patents, Awards

Our innovative and forward-thinking approach to designing products has solved wet basement problems that the basement waterproofing and crawl space industry has faced for decades, and our patented sump pump systems are the smartest and most reliable. Plus we listen to our customers and respond accordingly! Basement Systems Inc. has been awarded 24 Patents and 19 Innovation Prizes on waterproofing products we use every day, including a battery back up sump pump system. This approach ensures the best waterproofing systems and solutions available.

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