Subfloors & Underlayments

1. Above/Suspended – A suspended floor is one with a minimum of 18″ of well-ventilated air space below.
2. On grade – An on-grade floor is in direct contact with ground or over a fill in direct contact with ground.
3. Below grade – A below-grade floor is partially or completely below the surrounding grade level in direct contact with the ground or over a fill in direct contact with the ground.