How far below the grade must exterior insulation board extend?

Exterior insulation board must extend a minimum of 12 inches below the grade level to ensure that it is adequately protected from moisture and soil exposure. This extension is crucial because it helps prevent damage from water intrusion, which can lead to mold growth and structural issues within the wall assembly. Insulation that is not sufficiently protected can lose its thermal efficiency and may deteriorate over time due to moisture exposure.

When insulating a building from the exterior, it is also essential to consider the building's drainage systems and how water is managed around the foundation. Having the insulation extend below grade allows for a better integration with landscape drainage solutions and contributes to the overall energy efficiency and longevity of the building's exterior wall system. Proper installation practices, including the depth of insulation below grade, are vital in meeting building codes and standards.