Void In Footers
One of the main elements that EVstudio Inspectors look for when observing footers is that void is present where it is called out on the site-specific plans. Void systems, when incorporated in footings, create a buffer zone between expanding soils and concrete foundations. Additionally, void systems support the weight of the concrete and construction loads throughout the construction process until the concrete has enough strength to span between supports. Void systems allow heave from expanding soils below and around the foundation to occur without detrimental effects to the foundation structure.
The most commonly used void systems here in Colorado are Degradable void systems and Collapsible void systems.
- Degradable void form systems are typically constructed of a corrugated paper product arranged in an open cell pattern. The exterior surface of the void forms is coated in wax to initially resist moisture from the soil, concrete, and weather. These forms will degrade over time and allow expanding soils to move into the spaces left without causing structural damage to the foundation.
- Collapsible void form systems are made of non-degradable material designed to collapse from soil pressures heaving from below that are greater than the foundation structure dead load. These systems are designed, however, to withstand the construction process of concrete placement. The materials used for collapsible void systems usually consist of plastic, wax-impregnated corrugated paper, or other moisture-resistant materials designed to collapse under bulging soil pressure.
Other uses of a void that EVstudio Field Inspectors look for are that there is one (1) foot of void placed under all windows and that void is placed per plan – usually 12’ on center throughout the footer for installation of perimeter drains.
EVstudio Field Inspectors pay close attention to the details of the site-specific plans to ensure all void is placed where necessary. To learn more about EVstudio’s Field Services click here.
Websites Referenced
http://www.foundationperformance.org/Projects/FPA-SC-11-0.pdf
http://www.foundationperformance.org/pastpresentations/SkollerPres-9Jan08.pdf
