Posts Tagged ‘sinkholes’Posted on: May 10th, 2012 No Comments
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
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:
- Shallow groundwater in upper five feet of borings.
- Voids or very soft conditions encountered within the limits of the borings.
- Buried organic material or heavy organic debris.
- Pipe Clay, aka Fat Clay.
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.