Reducing Radon in New Construction of ANSI/AARST CCAH 2020 1 & 2 Family Dwellings and Townhouses 10 403.2.6.1.3 Penetrations. Openings in the soil gas retarder membrane for piping, utilities, structural posts and similar penetrations shall be sealed. 403.2.7 Penetrations. Penetrations through the concrete slab and soil gas retarder shall be sealed with a caulk complying with ASTM C920 class 25 or higher or a method recommended by the membrane manufacturer. 403.2.8 Block-outs. Where openings are cast or constructed in the concrete slab under plumbing fixtures, the openings shall be filled with expanding foam or a non-shrink grout. Exposed openings shall be sealed with non-shrink grout. 403.2.9 Seal sides of the soil gas collection plenum. The intersection of floors and foundation walls shall be sealed with a caulk complying with ASTM C920 class 25 or higher. Sealing shall be performed in accordance with Section 403.2.9.1 or 403.2.9.2 or 403.2.9.3 or 403.2.9.4 or 403.2.9.5. 403.2.9.1 Seal floor to wall. The intersection of floors and foundation walls shall be sealed. 403.2.9.2 Seal soil gas retarder to footing or wall. Where foundation walls are solid concrete, the soil gas retarder shall extend from the footing up the wall not less than 4 inches [10 cm] and be sealed to the footing or to the foundation wall. 403.2.9.3 Seal soil gas retarder to wall. Where foundation walls are masonry block the soil gas retarder shall extend from the footing up the wall not less than 4 inches [ 10 cm] and be sealed to the foundation wall. 403.2.9.4 Soil gas retarder in a monolithic slab. Where the floors and footings are monolithic the soil gas retarder shall extend completely under the footing.