If you live near fault lines and experience earthquakes with any frequency, then you know what it is like to worry about the foundation of your home or office building. Fear not; there are usually plenty of building codes that regulate the construction of homes and buildings in earthquake areas. If you are considering building a new structure in these areas, talk to your foundation contractor about post tension construction. Here is why this is an ideal approach for creating a foundation in an earthquake zone.
Post Tensioning Pre-Stresses the Foundation
Grids of metal cable are created prior to the pouring of concrete. The cables are somewhat loose to start. After the concrete is poured and has started to set, all of the cables are pulled tight, stressing the concrete and creating slight fractures. The contractor then smooths and adds fresh concrete to the slab. The concrete is allowed to cure in this newly-tightened position. Then the cables are loosened. The concrete is now "pre-stressed," which gives it a little more "flexibility" during an earthquake and prevents breaking.
The Tension Grid Protects the Formation of the Slab
Imagine trying to pour and cure concrete and then an earthquake occurs. Without post tensioning, the uncured slab becomes uneven and possibly much more fractured than a concrete contractor wants. That is not the kind of foundation on which you want to set any structure. Typically, the entire slab would have to be ripped up and redone. If post tensioning is used, your concrete slab foundation is less likely to undergo a redo if and when an earthquake hits.
If Your Contractor Opts to Keep the Cable Grid Taut, It May Protect Against Big Earthquakes
With the post tension approach, you can either release the cables after the concrete has cured, or you can keep them taut. If your contractor opts to keep the cables taut, it may prevent your newly-constructed slab foundation from fracturing during a big earthquake. By extension, it may also protect the building on top of the slab. Only a structural engineer can tell you for certain, and he or she would have to look at the property on which the structure will be built prior to the contractor starting work.
Finding Your Contractor
There are any number of concrete contractors in your area, to be sure. However, if you decide to use the post tension approach to your new foundation, you will need a contractor that is experienced in this technique. Ask for references to other post tension projects the contractor has completed.