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Foundation Systems

Objective Comparison of Foundation Repair Methods

Bell-Bottom Piers vs. Hydraulically Driven Pilings

History

Bell-Bottom Piers

Developed about 40 years ago to temporarily stabilize residential foundation movement in most soils and for most loads.

Pilings

Developed over one thousand years ago in Europe to build, level and stabilize any number of structures. Currently used extensively in the construction of bridges, skyscrapers, etc. About 20 years ago, Structural Engineers at Texas A&M, among others, thoroughly tested and secured FHA/VA approval for residential foundation repair application. Reinforced concrete pilings are now the industry standard.

Regulation

Bell-Bottom Piers

Fully approved by FHA, VA and Conventional lenders, and all City Codes.

Pilings

Fully approved by FHA, VA and Conventional lenders, and all City Codes.

Warranty

Bell-Bottom Piers

Lifetime Service Agreement: Free adjustments for the first 10 years, then $45.00 per pier, for the life of the structure. Some restrictions. Transferable one time.

Pilings

Lifetime Transferable Warranty: Free adjustments for the lifetime of the structure. Unlimited, no cost transferability.

Engineering Requirements

Bell-Bottom Piers

Pier depth and bell diameter are critical. Extensive soil testing and load evaluation must be completed prior to determining the exact pier size and cost. Pier holes must be inspected by a registered engineer for correct depth, bell size and reinforcement placement before concrete can be poured. Approximate soil lab cost: $800 – $2000. Engineer provides job completion certification letter attesting to all inspection results.

Pilings

Pre-engineered to test soil capacity and load requirements as piling is hydraulically driven into the ground. No soil test required. Pre-tested and certified with a minimum three-to-one safety factor. Piling depth and pressure readings are logged and recorded on the final completion drawing. Engineer reviews and stamps final drawing.

Life Expectancy

Bell-Bottom Piers

Properly engineered, designed, inspected, and installed piers will have an adjustment rate of approximately 90% within the first 10 years. (Industry Average). The industry average failure rate: 8%. (8% not re-usable after 10 years).

Pilings

Properly driven, 6″ x 12″, reinforced cylindrical pilings will have an adjustment rate of approximately 1% within the first 10 years. There is no failure rate for correctly installed, reinforced cylindrical pilings.

Job Time

Bell-Bottom Piers

Usually about one month due to piers being made on-site. Requirement for curing 3000 PSI concrete, of 28 day test as per ACI Standards, routinely waived by on-site foreman to expedite job. Additionally, rain can cause un-poured pier shafts to fill with water and collapse. This can cause major time delays. Calculating clean-up and weather delays, some jobs can take up to 60 days, or more, to complete.

Pilings

Usually 3 to 5 days. Requirement for curing 6000 PSI concrete of 28 days, as per ACI Standards, exceeded, as all blocks and cylinders are pre-made and batch stress tested and certified at the factory before shipping. Speed with which piles are driven precludes any rain delay problems, except “actual raining time” delays.

Mud Pumping

Bell-Bottom Piers

Mandatory in all situations to minimize “initial settlement” load transfer problems during the first four to six months after job completion. Frequently leads to additional problems such as swelling and interior heaving.

Pilings

Variable applications. Due to three-to-one minimum safety factor inherent in piling installation, initial settlement problems are negligible. Usage determined on a case by case basis at the time of the job. No heaving or swelling problems.

Landscaping

Bell-Bottom Piers

Long job time and heavy equipment required can destroy lawns and shrubs.

Pilings

Shorter job time and no heavy equipment required, drastically reduces re-landscaping problems and costs.

Remedial Repairs

Bell-Bottom Piers

Recommended minimum wait of four to six months after job completion before any repairs, (doors, sheetrock, painting, plumbing/sewer, tile, mortar, etc.); due to initial settlement after load transfer and possible heaving. Tunneling is not available for interior pier installation.

Pilings

Thirty to forty five day maximum recommended waiting time after job completion, to allow structural members to absorb the stresses of leveling. No initial settlement or heaving problems. Doors, plumbing/sewer lines, mortar cracks, and other items not affected by re-alignment can be repaired immediately. Interior pilings can be installed via tunnels, eliminating the need for costly floor replacements and/or repairs, and to minimize interior clean-up requirements.

Foundation Specialists, Inc.
4424 W. Sam Houston Pkwy N.
Suite 440
Houston, TX 77041
Fax: 713.690.9220

Main Office Phone: 713.690.5330

Dallas Office:  972-239-4374
Austin / San Antonio Office:  512-291-4374
Houston Office: 713-690-9220

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