What is the typical grossing factor for a classroom?

• A. 1.1
• B. 1.5
• C. 1.75
• D. 2.0

Answer: (B)

The idea behind a grossing factor is to convert net usable space into the total built area by accounting for walls, circulation, restrooms, mechanical rooms, and other non-programmatic spaces. For classrooms, a factor of about 1.5 is commonly used because it adds roughly half again as much space to cover these supporting areas. So if you start with a net classroom area, multiplying by 1.5 gives a realistic gross area that includes needed circulation and services. Using a smaller factor like 1.1 underestimates these spaces, while larger factors such as 1.75 or 2.0 tend to overestimate for typical educational buildings. For example, a 600 sq ft net classroom would be about 900 sq ft gross with a 1.5 factor.