The Enemy of the Slab Foundation – Voids
At Foundation Repair Pros, we know slab foundations in Fort Worth and the DFW…inside and out! We have a group of professionally trained technicians that specialize in the various patented technologies that are used to correct slab foundation deficiencies. First, let’s offer a little background…
By far, the slab foundation is the most widely built and popular foundation in the U.S. and beyond and for good reason. If built on a properly prepared building site and if it is well maintained, it is a very stable platform for your house. And one more benefit – the foundation is about 2-2 ½ times cheaper to build compared to a pier and beam foundation. There are 3 basic designs for the slab with the monolithic pour the most common in our area.
But slab foundations can have their problems. The #1 enemy is voids that develop underneath the slab, between the bottom of the cement and the soil. The absence of support weakens the cement leading to cracks and eventually total failure.
The Top 3 Causes of Slab Foundation Failure
- Highly Variable Soil Moisture – periods of persistent drought causes the soil to dry out and shrink, reducing the density and strength of the soil to support the foundation. Voids are created allowing the foundation to settle and break. This is particularly a problem around the perimeter of the house but may extend to interior walls. Trees and large shrubs near the foundation can also drain the soil moisture, further reducing density and strength.
The opposite is also a problem – too much moisture can cause the soil to swell and expand upward causing similar pressure points resulting in heaving and cracks. Improper drainage around the home is the most common contributor to this problem
- Poorly Compacted Soil During Construction – builders have to prepare a level building lot which requires moving dirt around the site. The most important step is to tightly compact the soil prior to laying the foundation. This includes having well compacted soil beneath the footings.
This is accomplished by carefully layering clean fill (free of organic material) with 3-5% moisture content and the use of a compaction roller or a heavy duel axle dump truck. The compaction should be measured by a geo-technical engineer to achieve 95%+ Standard Proctor Density.
When these steps are not executed carefully, voids develop and the foundation cracks and settles.
- Plumbing or Sewer Line Leaks – similar to the external drainage problem, a plumbing or sewer line leak under the slab will push soil away from the leak area creating a void. Sewer line leaks, if persistent over time, can also cause expansive soil swelling resulting in lifting the home or creating a domed section in the floor. Certainly, these leaks need to be corrected to insure the long-term integrity of the home and the foundation.
Techniques for Slab Foundation Repair and Leveling
Many foundation companies in the DFW area offer a “one-trick pony” solution i.e. steel piers and that’s it. Either you agree to steel piers (which are slightly higher priced but extremely effective) or they don’t do the work. That’s good for us because Foundation Repair Pros offers many repair options that can be tailored to meet any budget constraint and yet provide a Lifetime Transferable Warranty on all of our slab repair projects.
Here’s an overview of the techniques available in our arsenal:
External Drainage Management – several options including French drains, swales and moisture barriers to eliminate ponding water adjacent to the foundation.
Void Management – mudjacking or urethane injection is used to fill voids and lift light weight concrete structures like sidewalks, driveways or pool decks.
Root Barriers – provides a physical barrier between tree roots and the foundation. A trench is dug parallel to the foundation and a specialty geotextile, bio-barrier is secured. Designed to eliminate tree root intrusion while allowing water movement.
Helical Piers – although first used to support English lighthouses in 1833, this technique has evolved into a highly technical process. A helical steel pile is augured up to about 20-25 feet in the DFW area with an engineered rotational torque specification and shaft size. Excellent for areas with limited access.
Steel Piers – without question these are the most effective, optimal, permanent solution for slab repair. While slightly more expensive than some piles or piers, these have proven themselves nationwide as the preferred alternative. These are driven to confirmed bedrock which is in the range of 20-50 feet in the DFW area. These can be used around the perimeter or on the interior.
Concrete Pressed Pilings – the most commonly used technique in the DFW area, this involves driving a stack of concrete cylinders (6-8” diameter x 10-12”) to refusal (12-15 feet). The concrete is cured to withstand about 7,000 psi and can be reinforced with cable or re-bar. A small hydraulic ram is used to drive the pilings.
Poured Concrete and Belled Piers – an excellent permanent solution where reinforced concrete is poured into a augured shaft 10-20 feet and allowed to set for 7-10 days. Technique frequently includes a belled area at the bottom of the shaft (30”) which significantly increases the load bearing capacity of the pier.
Foundation Repair Pros – The Company of Choice
Foundation Repair Pros has established itself as the industry leader in innovative techniques to tackle slab foundation problems. As discussed above, there are a multitude of physical variables that influence the stability of a slab foundation. Each of these variables must be evaluated in order to develop the best technical and economic solution for a particular home.
Give us a call today to schedule our free foundation inspection. Demand for our inspection service is high so you’ll need to book a date in advance.
We look forward to earning your trust and solving your foundation issues!