Repair Wood Damage

Repairing Floor Joists & Girders In Your Crawl Space

Symptoms of Sagging Floor Joists and Girders in a Crawl Space:

Problems related to inadequate floor joist bracing can show up all over the house, including the following:

  • Sinking/Uneven Floors
  • Springy Floors Underfoot
  • Cracks Forming On Interior Drywall
  • Jamming/Sticking Interior Doors
  • Moldy Floors
  • Sinking Crawl Space Supports

If your home has sagging floor joists and girders, you're dealing with a problem that manifests itself throughout the entire building.

A problem such as this can be caused by many possible factors, but are usually the result of three common issues:

Inadequate Supports: The support system under your home has too few support posts to hold up the structure.

Weakened Floor Joists & Girders: Moisture, rot, termites, wood-boring insects, or other destructive forces have damaged your structural wood.

Support Settlement: Weak supporting soils underneath the crawl space supports have caused the crawl space supports to sink into the ground.

What's Damaging Your Floor Joists & Girders?

If Mother Nature is the cause of your damage, there can be many possible forces hard at work on your crawl space's structural wood. Determining which one you're dealing with can be difficult to do!

Sometimes, a wood surface can be virtually covered in mold, but will still show little evident structural damage. In other cases, the wood may appear to be strong and untouched, while subterranean termites have hollowed the wood out from the inside.

Before you can consider a permanent repair for your crawl space, you will need to address the moisture and humidity that feeds mold, rot, pests, and other unwanted forces in your crawl space. The key to this is to keep your crawl space dry by installing a crawl space vapor barrier system and by running a powerful crawl space dehumidifier system.

The slides below feature six common ways that floor joists and girders in crawl spaces can be damaged.

A  Simpsonville crawl space support system repairing a sagging structure.

Crawl Space Floor Joist Jacks

Crawl space joist supports are steel, adjustable support posts that are installed to repair sagging floors.

These reinforcing joists install quickly in crawl spaces -- with a complete installation taking about a day -- and provide a permanent solution.

Our SmartJack® Support System is designed with corrosion-resistant galvanized steel, ensuring that it will be strong and adjustable for decades to come. A unique base of engineered fill prevents sinking support posts when soils below are weak, maximizing effectiveness.

More about our Crawl Space Jacks

Reinforcing Joists & Girders

Compared to other sources of structural damage (frost heave, foundation settlement, bowing foundation walls, etc.) it's relatively easy and inexpensive to reinforce joists and girders in a structurally damaged crawl space.

Girder and joist jacks (also known as "steel lally columns") can be installed at key locations along the structure. Once in place, the floor can be "jacked up" in an attempt to lift the floor back to a level position. If a contractor finds a joist is severely damaged, a sister beam can be installed alongside the normal one for extra strength.

At Cantey Foundation Specialists, we've seen just about everything! Below are just a few of the sagging floor joists the experts in our network have encountered:

(Click to see a larger view.)

A repaired floor joist in a Mount Pleasant crawl space. A collapsing crawl space support in a Greer home.
A crawl space support consisting of a rock and wood shimming in a Augusta home Rusty steel crawl space jack post supports in a structure in Greenville.
Old, corroded crawl space jack posts in Charlotte.

Light-duty joist braces, such as are found in big box stores throughout South Carolina, North Carolina and Georgia, should not be as permanent supports.

These joist braces are made out of steel that can rust and corrode, making them difficult or impossible to readjust if the support post sinks down in the soil.

The "Bulb Of Influence"

No matter how strong your floor joist supports are, they can only bear as much weight as the soils underneath them. Put simply, if the supports are sinking, your floor is going to sink with them.

To address this, our contractors take advantage of something called the "bulb of influence".

Before we install your support posts, we excavate a 2' cube hole, filling it in with compressed, crushed stone. Then we place a concrete base on top of the center of this cube and position the jack post above that.

This cube of compressed, crushed stone disperses the weight pressing down into the soil outwards, dispersing it to approximately 10% of the pressure present at the bearing surface.

This means that even if the soils under the jack posts aren't strong enough to support great weights, your system will still be more than sufficient to support the structure above.

How Do Other Floor Joist Support Methods Measure Up?

There are many different methods of crawl space repair that contractors are using today, and some are much better than others, but all of them work at least some of the time.

Of course, if these repair methods never worked, then they would not be used anymore. However, at Cantey Foundation Specialists, our reputation and written warranty depend on using solutions that will be permanent -- and will work all of the time. The chart below lays out the facts:

Girder & Floor Joist Support Solutions


Additional Shimming

Concrete Masonry Unit (CMU) Columns

Light-Duty Jack Posts

The SmartJack® Crawl Space Jack System

Provides a solution for floor joist bracing that is spaced too far apart to provide proper support

black X green checkmark green checkmark green checkmark
Can be combined with a moisture barrier system to repair sagging floor joists and girders that are damaged by rot and mold black X green checkmark green checkmark green checkmark
Are appropriate for installation in areas where the soils cannot support heavy loads, and would normally cause joist supports to sink black X black X black X green checkmark

Can be installed without "over lifting" the foundation, which is known to cause additional structural damage

black X black X green checkmark green checkmark

Adjustments can be easily and reliably made, should the joist brace settle into the soil

black X black X black X green checkmark
Installs in the home within a day green checkmark black X green checkmark green checkmark

The girder jacks and joist jacks provide a high load-bearing capacity for structural support

black X black X black X green checkmark

We Repair Sagging Floor Joists & Girders In Crawl Spaces!

At Cantey Foundation Specialists, our experts have the experience, training, and warrantied products that you're looking for! With a fast, noninvasive installation, we can provide a lasting solution for your home that will restore your structure and avoid further, potentially expensive, damage.

It costs you nothing to meet with one of our specialists for a professional inspection and written cost quote! To schedule a Free Estimate, contact us by phone or e-mail today!

We proudly serve the South Carolina, North Carolina and Georgia area, including Charleston, Columbia, Charlotte, Greenville, Augusta, Mount Pleasant, Concord, Simpsonville, Spartanburg, Greer, and many surrounding areas.

Additional Shimming

When additional shimming is added to a crawl space support, the floor must first be mechanically lifted to above its original position with temporary jacks. This overlifting can potentially cause structural damage to the home.

Next, pieces of metal or wedges of wood are inserted into the gaps at the top of the support columns. Then, the structure is lowered on top of the shims, and the jacks are removed.

If your crawl space is sagging because they're rotting, it will continue to rot after the repairs are made.

If too few girder and joist supports are the cause of the sinking, the floor will continue to be poorly supported, and will continue to sink. If the columns have sunk because the soil was too weak to support the weight, they will probably continue to sink.

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Wedges of wood used as shimming for crawl space floor joist bracing

CMU Columns

Sometimes, a contractor will reinforce joists in a crawl space by adding additional concrete columns. These concrete blocks will be custom-made for the crawl space, and will need several days for the grouted-together block mortar to cure.

Next, the crawl space will be jacked upwards using temporary jacks, and the concrete blocks will be put in place. Shimming will be used to fill the gaps at the top of the column. During the shimming process, additional structural damage may occur.

If you have sagging floor joists in a crawl space due to rot, it will continue to sag after the repairs are made. Replacement beams will rot as well, unless the moisture issue in the crawl space is addressed. If the columns have sunk because the soil was too weak to support the weight, they may continue to sink into the soil.

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A Concrete Masonry Unit Column, also known as a CMU Column being used for sagging floor repair.

Light-Duty Jack Posts

Light-Duty Jack Posts are adjustable steel posts that are used to add support in a crawl space, and are typically installed on top of a concrete block on top of the soil.

During installation, the floor joist bracing post is extended until it reaches and supports the sagging girder. These posts typically have a low load-bearing capacity (15,000-18,000 pounds).

Over time, they will begin to rust and corrode, weakening the post and making it difficult or impossible to adjust.

If your crawl space is sagging due to rot, it will continue to sag after the repairs are made. If replacement beams are installed that are not rotting, they will eventually rot as well. If the columns were sinking because the soil was too weak to support the transferred weight, they may continue to sink.

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A floor joist support or joist brace system

The SmartJack® System

The SmartJack® is an adjustable galvanized steel (corrosion-resistant) girder and joist jack that is used to support a crawl space. It sits on top of a pre-cast concrete block. Underneath the block, a 2' by 2' cube of soil is removed and replaced with an engineered stone fill.

The jack post is extended to the girder or joist, halting movement. The SmartJack® is adjusted to attempt to lift the floor back to its original position -- a process that will not cause structural damage.

If sagging is occurring due to rot, new sister beams will be installed. The SmartJack® will not sink due to poor supporting soils due to the base of engineered fill, which disperses the weight to 10% of what it was.

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The SmartJack® steel lally columns system

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Cantey Foundation Specialists
621 Rutledge Street
Camden, SC 29020

Cantey Foundation Specialists
621 12th Street
Augusta, GA 30901

Cantey Foundation Specialists
4225 Piggly Wiggly Dr
North Charleston, SC 29405

Cantey Foundation Specialists
5951 US-221
Roebuck, SC 29376

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1508 Industrial Dr
Matthews, NC 28105
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