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## Why is a roofer's estimate of the square feet of roof area so much higher than the square feet of a house?

Tuesday, October 29, 2019

If you were stunned when your roofer quoted you for a 3200 square foot roof for your 1800 square foot house, here’s why:

1) Homes usually have two different square footages listed on a realtor’s listing sheet or the tax appraiser’s property records. One is the conditioned (heated and cooled) living area—which is what most homeowners think of as the square footage of their home—and the other is the total area under roof. A typical home that the owners know as being 1800 square feet may also have a 450 square foot two-car garage, plus front and back porches that total another 300 square feet, for a total of 2500 square feet under roof.

2) But that’s just the beginning.  That 1800 square foot house typically has a two foot roof overhang that adds an average of 250 square feet of roof, for a total of 2750 square feet.

3) Then the pitch of the roof adds more area. A 6/12 pitch roof (6 inches of rise for every 12 inches of run) has approximately 117 square feet of roof over every 100 square feet of floor below. In this case, the pitch would tack on an additional 450 square feet. That makes a total of 32 squares of roof for an “1800 square foot” house.

4) Roofers calculate roof area in “squares,” with a square being 100 square feet of roof area. When you get a price for a new roof, the contractor may say something like “the roof works out to 32 squares and will be \$9,500.”

• • • • • • • • • • • • • • • • • • • • • • • • • • • •

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