Roofing Square

A square is the standard unit of roof area in the United States and Canada. One square equals 100 square feet, or about 9.3 square metres, of finished roof surface. Shingles, metal panels, underlayment and labour are commonly priced and ordered per square, and roofers describe roof sizes in squares (for example, "a 25-square roof").

Coverage, not product area

A square of roofing material is the amount needed to cover 100 sq ft of roof once installed with the intended overlaps. Because shingles, shakes and tiles overlap, the actual area of product in a square is greater than 100 sq ft. Asphalt shingles are packaged in bundles, and the number of bundles that make one square varies by product and is printed on the packaging.

Waste from cutting is not included in the square, so estimators add a waste factor on top.

Converting measurements

• Squares = roof area in square feet / 100.
• Square metres = squares x 9.29 (approximately).
• Plan (horizontal) area must first be converted to sloped area with a pitch multiplier.

Example: a roof with 2,350 sq ft of surface is 23.5 squares, or about 218 m².

Other uses of the unit

The square is also used for siding and some other cladding products in North America. In Australia, the square was historically used for house floor areas and is still sometimes used in real estate in Victoria, but construction there now uses square metres. In most other countries, roofing is measured and sold in square metres.

Related unit in low-slope roofing

Application rates for bitumen and coatings in North America are often given per square, for example pounds of asphalt per square, alongside metric rates in kilograms per square metre.