Before the boxing and digging begin, a 15 to 18 foot soil test is performed to determine the correct depth for your new bell bottom piers. It is imperative that these piers are secured in stable soil and the soil test will establish the depth needed to reach stable soil. Without a soil core test the foundation repair contractor is simply guessing the depth needed to reach stable soil.
Soil Core Samples being Drilled and Tested
The soil core test will show the foundation repair contractor and homeowner the depth that must be reached to allow installation of piers in stable soil. A test hole is drilled near the foundation and soil samples are extracted at various depths.
The foundation repair contractor should take soil core samples at various intervals to confirm the correct level of stable soil. Generally soil core samples are taken at 8, 10, 12, and 15 foot levels. In the Houston area stable soil is usually reached at the 12 – 15 foot level.
The soil core samples from various depths are tested with a specialized tool to determine their load bearing capacity. Usually when stable soil is reached it will support approximately 3.0 to 4.0 tons per square foot. Once the depth of stable soil is determined then the foundation repair contractor can instruct his crew to dig holes to the proper depth.