Roofing Equations for Figuring the Square

Roofers refer to roofing installation in "squares".

The roofing industry and everyone in between have always figured roofing in squares, which equals 100 square feet. This method is interchangeable and understood by roofing contractors and building suppliers. In order to figure roofing squares, you must follow a few simple steps of measurements and calculations, which can be done by the average do-it-yourselfer in 1 to 2 hours, depending on the size and scope of the project.

Measurements

Measure the length and width of the roof, including overhangs and extensions, using feet for all measurements. Your roof surface to be measured is defined as any surface that will be directly exposed to the elements, such as rain, wind and snow. Measure all sides of the roof. If your roof is gabled, then measure the roof on each side of the gable, and if yours is a hip roof, then measure the surface on each side of the hip.

Recording

Record all measurements on a sheet of paper under separate headings. For example, record both sides of a gabled roof under sections such as "Roof 1" or "Roof 2." This will help keep your measurements organized and prevent your having to measure the entire roof again if you need to change a recording.

Multiplying

Multiply each section's length by its width. This will be your total square footage for the respective section. Add all multiplications together to get a total square footage for the roof. Make a "total" column and record the total roofing square footage.

Totals

Divide the total square footage by 100. For example, if you have 1,000 total square footage of roofing space, then divide that to get a number of 10. This represents the total number of squares needed to cover your roof. Multiply the total squares by 5 percent to account for waste. For example, 10 squares multiplied by 5 percent equals (10)(0.05) = 0.5 square. Round up, in this case adding 1 square to the total, and you have 11 squares.

References

• "Roofing Construction & Estimating"; Daniel Benn Atcheson; 1995
• "The complete guide to Roofing & Siding: Install, Finish, Repair"; Creative Publishing International; 2004
• "Miller's Guide to Framing & Roofing" ;Mark R. Miller; 2005