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How to Measure a Roof and Determine How many Squares of Shingles are Needed 

When installing a new roof or paying a professional roofer, the magic number is the number of “squares of roofing shingles.” A square of roofing is equal to 100ft2 of asphalt shingles. Roofers will typically charge based on the number of squares of roof in need of installation. Other factors include whether the roof can be walked upon without ropes. If a roof does not require cable for workers to be safe, it is called, “walkable.” And vice versa, “non-walkable.” If a roof already has a layer of shingles, another layer of shingles can be laid-over the old layer of shingles. The shingle installation is called a “lay-over.” Obviously a lay-over cost less because the labor and dumping costs are less.

calculate roof squaresMeasuring and estimating how many squares of shingles you need is fairly easy and simple. First you will want to calculate the length and width of the different sections of your roof. Most smartphones have a measuring feature installed that makes it very simple and easy to do so. Once you have your measurement for the length and width of the different parts of your roof you will now want to multiply those together to get the area of the different parts of your roof. Once you have calculated the areas of each part of the roof, add up the different areas to determine the total surface area of your roof. Now take the square footage of your roof and divide it by 100 to determine the total squares of shingles you need to cover your roof. Three bundles of shingles will cover a single square. For example if your roof was 1900ft2, then you would have 19 squares and need 57 bundles of shingles to cover it. When installing a new roof keep in mind there is approximately 10% waste. So, if you are installing a 1900 ft2 roof, you should order an additional 200ft2 of shingles.