Floor Grades: Understanding Installation Limitations

Hardwood flooring installers break down any home into three separate sections that determine which types of hardwood flooring in specific locations. These sections are called floor grades. There is “On Grade,” “Above Grade,” and “Below Grade.”

Installation Grades


On Grade: This section applies to all levels of a home which are at ground level.

Above Grade: This section applied to all levels above ground level such as second and third stories and so on.

Below Grade: This section applied to all levels that are located below ground level. This is true for rooms that only have part of the room below ground level. For example, basements are always “Below Grade” even if part of the basement is open to a different part of the ground level. This is common in homes where part of it is built in the ground and above ground level. Other common examples include partial underground basements and partial underground garages, and split level homes that are built directly into a hillside.


Each grade level contains different types of hardwood flooring that can be installed.

On Grade: Levels that are completely ground level can have solid, engineered or floating hardwood flooring.

Above Grade: Levels that are above ground level can have solid, engineered or floating hardwood flooring.

Below Grade: Levels that are beneath the ground level, even partially can only have engineered or floating hardwood flooring. This is because these levels are highly susceptible to moisture issues. Solid hardwood flooring is more susceptible to moisture issues because solid wood and water don’t mix.


Any room in the house that is highly susceptible to moisture exposure or issues should avoid solid wood hardwood flooring regardless of which level the room is on. For example, bathrooms and laundry rooms are common places where solid hardwood flooring should be avoided even if these rooms are located on a second or third level of the home.