How to Seal for Radon With a French Drain

Radon, an odorless, colorless, radioactive gas, is a major cause of lung cancer. Radon may seep into a building through cracks or openings in a French drain, an interior footing drain that utilizes a gap between the interior wall and floor. A cove base is a contoured molding intended to fit over and seal the joint between the wall and the floor. In order to mitigate the effect of the gas, a "suction field" is created whereby polluted gas is sucked out of the ground and out of the building in pipes that vent high, well away from any re-entry points into the structure.
The method, called a sub-slab depressurization system, requires the French drain and all other cracks, holes, intruding pipes, and sumps to be sealed. If the French drain or other through-slab intrusions are not sealed, the pressure is reversed and the fan sucks air back into the ground.

Instructions

1. Make an Inspection

   • 1

     Check the concrete slab floor for cracks, holes, openings around pipes and other intrusions.

   • 2

     Inspect the French drain for a gap between the walls and the slab.

   • 3

     Determine whether the sump pump is a radon-sealed pump.

   • 4

     Check the sump for gaps around the pump.

   Seal Openings

   • 5

     Clean and dry the areas to be sealed with a vacuum cleaner or oil-less compressed air.

   • 6

     Prime the areas to be sealed with Radon Crack-Weld or similar product.

   • 7

     Fill the cracks, holes and gaps with dry sand.

   • 8

     Soak the sand with Crack-Weld.

   • 9

     Replace non-radon sealed sump pump with a radon-sealed pump.

   • 10

     Install and seal a cove base over the sealed French drain.

   • 11

     Seal off existing cove bases and all pipe intrusions and wire chases with Pipe-Tite or similar sealant.