Radon: Pre-Construction Considerations
Radon is a radioactive gas that is produced from the decay of naturally occurring uranium in the soil, rock and water. It chiefly enters buildings through cracks, joints, penetrations and gaps in the buildings floors, walls, plumbing, etc. Radon gas is more prevalent in certain areas of the State of Florida than others, but it has been observed in buildings throughout the State. The Environmental Protection Agency’s (EPA) “Building Radon Out” Publication (EPA/402-K-01-002), the State of Florida’s Department of Community Affairs Radon Program’s “Florida Standard for Passive RadonResistant New Residential Building Construction- July 1, 1995” and “Florida Standard for Radon-Resistant New Commercial Building Construction- January 23, 1996” should be referred to and followed during the initial planning stages of the construction project through completion.
The Florida Department of Community Affairs standards establish requirements regarding the sub-slab membrane material(s) and proper installation. The standards require the installation of a single layer of at least 6 mil polyethylene with a maximum perm rating of 0.3 as a soil-gas retarder membrane. PVC, EPDM, neoprene or other non-deteriorating, non-porous materials may be used under certain conditions. The membrane should be placed over the entire soil-contact area and care should be taken to limit seams, joints, penetrations and damage to the membrane.
Tape and/or mastic should be used in conjunction with the membrane installation at penetrations, seams, cuts, punctures or tears. The standards should be referenced regarding particular installation scenarios. A minimum 12 inch overlap should be maintained at membrane seams when concrete is placed. If the soil- gas retarder membrane needs to be sealed within 24 inches of a soil-depressurization system mat or pit only tape may be used.
The standards establish requirements for concrete strength, shrinkage, mix, curing and sealing. Concrete slab joints, penetrations, stakes, sumps etc. all require special considerations to limit gas intrusion. The standards also specific wall, crawl space, ventilation system and soil depressurization systems construction standards. Architects, Engineers, Ventilation, Building and Radon Mitigation contractors alike should study and follow these standards to limit radon gas entry into the new structures built here in the State of Florida.
