CC-1000_2018

CC-1000 Companion Guidance (1-2018) CC-1000 Companion Guidance CG Page of 12 Informational 5 Unified Soil Classification System (ASTM D 2487) CC-1000 Discussion 5.5 Gas permeable layers 5.5.2 a) Gravel or crushed stone Abundant hydraulic conductivity exists with mostly 3/4 inch stones in aggregates classified in ASTM C33 numbers 5, 56, 57 or 6. These products are commonly used in building construction. A complete hollow void under a building would require the least amount of energy for controlling the destiny of soil gas. Inversely, solid clay is impervious to air movement. Expansive soils or soils that contain more than 35% sand, fines, clay and silt are not considered gas permeable under CC-1000. 5.5.2 b) A void space The open void under membranes placed over soil in a crawl space. Engineered voids such as raised floors over concrete or soil.