Allow yourself plenty of time to calculate the quantity of shingles, underlayment, flashings, and other materials needed to roof a house. The more accurate your count, the less time you’ll waste waiting for material deliveries during the project.
UPDATE: Our new Roofing Calc iPad app based on this article is available now in the Apple iTunes store
In this excerpt, you’ll learn how to calculate the quantity of shingles you’ll need for a roofing job. I’ll describe two methods for determining the area of a roof and how to gauge the number of extra shingles you’ll need for waste, overlaps, and starter shingles.
Calculating the Shingle QuantityRoof shingles are sold by both the bundle and by the square. A square of shingles is the quantity needed to cover 100 sq. ft. of roof. Shingles are packaged in paper- or plastic-wrapped bundles designed to be light enough for a person to carry, so heavier shingles require more bundles per square. Three bundles to a square is most common, which applies to most three-tab strip shingles and some lightweight laminated shingles. Heavier three-tabbed shingles and laminated shingles require four, or sometimes five, bundles to cover a square. When shingles come three bundles to the square, there are 29 standard-sized shingles (12 in. by 36 in.) in each bundle.
Figuring out the roof area is the first step to determine how many bundles you’ll need to order. There are two ways to size up a new or freshly stripped roof: the measurement method and the sheet-count method. There’s a third method for calculating bundles when you’ll be laying new shingles over old or if the old roof is still in place.
Once you have a bundle or square count for the main roof area, you’ll add additional shingles to account for waste, starter shingles, and extra shingles for hip and ridge caps.