Posts Tagged ‘soil test’

Building a Home: Soil Testing

Posted on: July 16th, 2012 No Comments

The primary inspection that buyers of vacant land should perform after getting a contract is a soil test. Pipe clay, decaying organic matter and shallow ground water all pose a risk to the foundation of a home.

Daron marking the corners of the foundation.

Most soil testing companies will do four 10 foot borings as part of a standard residential soil test. Each of the four borings should fall within the footprint of the home that is yet to be built. After our initial builder consultation, we had a good working floor plan ready. It had been overlaid with a survey of the lot so we had accurate measurements of the foundation location. Daron (our builder) stepped off four corners and marked each with flourescent paint.

Next, we called a company to come out and test the soil. Using 10 foot augers, three technicians began boring holes on the four corners. Each handful of dirt that was removed from the ground was carefully scrutinized for any sign of trouble. A couple times they pulled what looked like clay from the dirt pile and each time my heart would stop.

Soil technician examining a boring sample.

Fortunately, nothing significant turned up in the test. There are solutions to fixing soil issues, ranging from reinforcing the foundation with additional rebar to excavating the site and back-filling it with workable soil.


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Soil Testing on Residential Property

Posted on: May 10th, 2012 No Comments

Soil boring being done on a vacant lot in Tallahassee. The orange mark under foot is where a corner of the home will be.

Tallahassee has some unique geological features that may make owning or building a home quite a headache. One of the first things you need to know is that our soil has characteristics of both Georgia clay and south Florida sand. It’s also important to know that there is much limestone throughout Florida that is constantly being dissolved and carried away by acidic rainwater. With these two things in mind, two soil problems quickly become evident.

Soil plasticity is the first thing you should have looked at if you are having foundation issues or are considering building a home on a vacant lot. Highly plastic soil is often referred to as “fat clay” or “pipe clay”. Soil with a high percentage of pipe clay can swell and become unstable when wet, then shrink by as much as 50% when it dries. This expansion and contraction can actually break concrete floors, crack walls and destroy the foundation of your home.

Sinkholes occur when voids left behind by dissolved limestone collapse. Sinkholes can be as big as those at the Leon Sinks Geological Area (several thousands of square feet) to much smaller areas. Sinkholes can cause your foundation to crack a little or a lot, and even make the home uninhabitable if the sinkhole is big enough.

Soil Testing a Vacant Lot

This tool allows testers to reach a depth of 10 feet

On unimproved lots, soil borings are taken within the proposed home footprint to provide a description of the soils encountered. Conditions of particular concern include:

Soil Testing Existing Structures

Soil tests can help identify problems that may have led to foundation problems such as differential settlement or movement resulting in the cracking or movement of the foundation, concrete block or brick veneer. Typically, cracking and movement within the foundation is found to be directly related to the presence of buried organic material, pipe clay, and/or  loose fill soils which were not properly compacted during construction. If testing reveals the cause of the problem, foundation system companies can help with foundation remediation.



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