Foundation Failure Topics:

- Why is it happening?

- Foundation Wall Cracks

- Sagging Floors

- Foundation Repair Methods

-Frequently Asked Questions

At Structural Design Solutions, we provide engineered foundation solutions to the Charlotte and surrounding areas of North Carolina and South Carolina.  The repair solutions listed on this page explained below to inform our clients of the possibilities for repair.  However, not all foundation settlement and crack issues require this type of repair.  These repairs are typically very expensive and should be only specified when needed.  Please contact us if you have any questions about these solutions or about a specific problems you may have encountered.

What can you do to repair your foundation

Foundation Stabilization Piers

Post installed stabilization piers are the most common solution prescribed for a settling foundation.  There are two basic types, concrete and steel.  The preferred type depends on the property soil conditions and accessibility.

Concrete piers are shown in the picture to the left.  The concrete pier system is composed of drilled concrete piers (designed by a professional foundation engineer) with a special bracket that attaches directly to the footing under the foundation walls.  This bracket then has the capability of lifting or jacking the footing or wall back to its level position if necessary.  If post-installed piers are only required to prevent future movements, then the piers are tightened under the footing.

Advantages to Concrete Piers:

• Installation of the concrete piers from the contractor's perspective usually requires less technical skills and less sophisticated equipment than the helical or push piers. 

• Concrete piers are poured on-site and have flexibility and adjustability

• Brackets have a large bearing area of concrete to rest, thus adding further stability, including reducing rotation at the bracket head

Disadvantages to Concrete Piers:

• Concrete piers require large amounts of soil removal, which must be removed from site

• Reinforcing bars and concrete must be placed carefully

• After piers have been poured, the concrete must be allowed to properly cure, thus increasing the time to complete the project

• Soil properties must be determined prior to drilled pier design

Helical piers are shown by the picture to the right.  These systems are typically composed of a anchoring rod (as shown above) and a foundation bracket.  The anchoring rod has an anchoring screws (number required by analysis) that propel the rod into the ground.  Upon reaching the appropriate torque resistant based on the calibrated ground properties, the helical pier installation is complete.  The brackets are then installed and the procedure is similar to that described above for the concrete pier system.

Advantages to Helical Piers:

• Much quicker installation time

• Due to the screw anchor properties, uplift and overturning forces can be resisted

• As the anchors are simply screwed into the earth, no soil disturbance is necessary

Disadvantages to Helical Piers:

• Requires more training to install and more expensive equipment than drilled piers

• Care must be taken to ensure minimal head rotation due to the anchor rods flexibility when subjected to lateral movements

• Typically more expensive than drilled piers

Push Piers are similar to helical piers.  However, push piers are designed to lift a house into a level position upon installation.  Push piers, hence the name, are pressed or pushed into the ground by a hydraulic pump.  The piers are typically installed along a wall.  In most cases, the entire house is retrofitted with these piers to achieve an equal force distribution along the foundation.  Once in place, the foundation brackets are attached beneath the footing or foundation wall.  Hydraulic pumps then push the piers into the ground until an acceptable load level is reached.  As mentioned before, in many cases, entire house foundations are retrofitted at one time.  Therefore, all the piers are hooked to the hydraulic pump at one time to ensure even force distribution.

Advantages to Push Piers:

• As the entire house is usually retrofitted with push piers, the house can be properly leveled as a whole

• Require smaller equipment to install because the house is used as the countersinking resistance

Disadvantages to Push Piers:

• Typically very expensive

• Driving pier force is the governed by the weight of the house, therefore only heavier loaded walls can be lifted

• Requires expert knowledge for installation

Wall Tiebacks are commonly used to restore structural integrity to basement or retaining walls that have been over-stressed or overloaded by lateral earth pressures.  As the wall begins to bow under the earth and soil pressures, it begins to crack horizontally.  There are many less invasive techniques that may be introduced to prevent or reverse further wall movement, however the wall tieback system is highly regarded as the best alternative under most conditions.

Wall tiebacks are basically rods that are anchored into the ground.  There are many different techniques that have been successfully used in the past for rod anchoring.  In most cases this requires digging behind the wall for securing the anchors.  Metal rods are inserted through holes in the walls, then directed to an excavated area of the yard where a large plate can be attached.  This plate is what produces the pullout resistance.  The metal rod has another plate at the wall end, which is secured by a nut and bolt assembly that can be tightened until the wall has reached its desired position.

Waterproofing and drainage are very important factors in the overall durability and structural integrity of soil retaining walls.  To begin, there are typically two methods for reducing water flow through a wall, waterproofing and damp-proofing.  Damp-proofing is a method used on less sensitive walls, which is basically a painted or sprayed material that sticks to the wall and once dry, increases the water resistance of the wall.  The second method, waterproofing, is a technique that uses a membrane (as shown to the right), which when installed properly, prevents water from passing to the wall completely.  The method of water prevention will depend on the sensitivity of the interior space and the wall use.

Drainage is key to a successful and long lasting wall design.  When water accumulates behind a soil retaining wall, unexpected pressure builds and may crack the wall allowing water to pass through.  However, if the wall is properly waterproofed and has improper foundation drainage, the structural integrity of the wall may be comprised.  Therefore, it is always a good idea to consult a professional engineer before construction begins or anytime after if you suspect an issue.