Why do foundations settle or sink?
Foundation settlement and movement can be caused by building on expansive clay, compressible or improperly compacted fill soils, or improper maintenance around foundations.
Whatever the cause, settlement can destroy the value of structures and even render them unsafe.
In any case, water is the basic culprit in the vast majority of expansive soil problems. Specific constituents of certain soils tend to swell or shrink with variations in moisture. The extent of this movement varies from soil to soil.
Those soils highest in clay content are generally more susceptible while those lowest in clay content are the least affected. In some areas the movement in insignificant; in others, it is quite pronounced.
When unstable soils are used as a base for a foundation, the tendency for movement is transmitted to the foundation. Since soil movement is rarely uniform, the foundation is subjected to a differential or upheaval. The problem shows up in both slab, and pier and beam type foundations.
If all the soil beneath a foundation or slab swells uniformly, there usually is no problem. Problems occur, however, when only part of the slab settles. Then, the differential movement causes cracks or other damages.
In residential properties, slab settlement problems can result in potential damage to the structure, potential accidents, and loss of real estate value. Poor drainage, tripping hazards, rough floors, unsightly cracks, and equipment malfunctions may also result from concrete slab settlement.
Interior and Exterior Warning Signs of Foundation Failure:
- Wall Rotation
- Separation around garage door, windows and/or walls
- Cracked bricks
- Broken and/or cracked foundation
- Displaced Moldings
- Interior Warning Signs
- Misaligned Doors and Windows
- Cracked sheetrock or Drywall
- Cracks in Floor
Past techniques for repair of sunken concrete has varied. Wood, concrete, cement and steel have been poured, pushed, turned or somehow forced into the ground trying to salvage these foundations and slabs, while early on, anyone and everyone, trained or untrained, became “experts” at this type of repair. Often as not, the repairs proved to be futile.
Other, more successful, methods of remediation involve extensive disruption of the family or business using the building. Usually, it is desirable that settlement of building slabs and monolithic foundations in residential areas be corrected without having to move all furniture, appliances, and possibly the whole family, or in commercial areas, without disrupting business. However, with todays technology and trained experts, there are a number of very successful solutions to the problem of sunken concrete that involve little or no disruption to normal living or business routine.
The two most common methods of this type of repair are slabjacking and hydraulic jacking (also known as piering).
In a slabjacking operation, grout is pumped beneath a slab or beam to produce a lifting force that restores the member to its original elevation. The repair method used depends on the type of distress being treated. The most commonly used method of correcting smaller slabs of sunken concrete, such as residential slabs, driveways, sidewalks, swimming pool decks, etc. is slabjacking. Slabjacking is done by pumping a cement grout through small, strategically-located holes in the concrete slab. Once in place, the grout solidifies into a dense concrete mass and provides a competent bearing for the concrete slab. If a soil-cement-lime grout is used, the lime content of the slurry will impart the benefits of lime stabilization to the base or sub-base. This combined treatment not only restores the slab to proper grade but also stabilizes the sub-soil to prevent re-occurrence of the problem. For larger problems, especially those found in house and commercial building foundation shifting, piering is typically used to lift and stabilize the foundation.
Piering involves the use of strategically placed mechanical jacks to lift the settled beam to grade. The beam must be raised carefully to avoid further or unnecessary damage. Once raised, the beam is held to elevation by a specially designed spread footing and pier.
The footing is set deep enough so that it will be independent of variations in soil moisture. It is also designed to adequately distribute the load without creating unnecessary bulk or mass. The pier is tied into the footing with steel and supports the foundation beam.
Piling or piering is the technique of driving steel pipe pilings to remedy failing building foundations and to correct foundation settlement.
Push piers consist of sections of galvanized or epoxy-coated steel pipe that are driven into the soil with a hydraulic ram.
Helical piers use screw piles with steel shafts. The lead section, with one or more helixes attached, provides the needed bearing capacity. The piers are screwed into the ground with a hydraulic torque motor.
With either system, one or more steel piers are driven to rock or a suitable soil bearing layer and are connected to the foundation through a metal head assembly. Once a suitable bearing stratum is reached, each pile is tested to a force greater then required to support the structure.
Hydraulic jacks attach to the embedded steel piers and are used to raise the foundation back to its original elevation. Once the structure is restored to the desired elevation the piles are affixed (bolted or welded) to wall brackets, locking the new elevation of the structure. Piers also offer an affordable solution for decks, porches, patios, hot tubs as well as pre-fab buildings.
Advantages of piers to correct foundation problems:
- Low cost. Up to ten times less than replacing the building foundation.
- No disruption or loss of use of the dwelling. The repair is performed with the building being used as normal.
- The equipment is portable and can be easily used in tight spaces or carried by hand where access is a problem.
- Remedies both the cause of the settlement (unstable soil) and the consequences (dwelling out of level) in one step.
- No yard destruction. No heavy equipment.
Slabjacking is an alternative to replacing sunken or uneven concrete, restoring sunken concrete slabs to their original grade. It is the process of raising or stabilizing faulty concrete pavement, and is performed on cracked and sunken concrete slabs such as driveways, steps and sidewalks, concrete pavement floors and other slab on grade surfaces. It is referred to as slabjacking when lifting or leveling is involved, or simply pressure grouting where void filling is the sole objective.
In the slabjacking process, instead of replacing the concrete, a cement slurry is pumped under the concrete. This process “lifts” the sunken and uneven surface back into its proper position. Performed properly, slabjacking can not only bring the concrete up to grade, it can also eliminate costly and irritating water problems by filling hidden cavities under the concrete and diverting water away from the foundation.
- Garage foundation repair
- Addition foundation repair
- House foundation repair
- Building foundation repair
- Playhouse foundation repair
- Deck foundation repair
- Sunken Concrete Repairs
- Sagging Floor systems
- Settling floors