It is a roofer’s term for 100 square feet of roof surface. When you get a price for a new roof, the contractor may say something like “the roof is about 28 squares and will be $8,000.” The area of roofing that is quoted in squares will be much more than you might expect for three reasons:

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, 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.

    Because a square is the standard roofer’s measure, rolls of roofing felt are sized based on squares. A roll of 30-lb. roofing paper contains 216 square feet, which is 2 squares after allowing for lapping. Bundles of asphalt shingles are usually 1/3 of a square. These sizes simplify the contractor’s computations when ordering materials.

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  To learn more about roofs and attics, see these other blog posts:

• Why is my roof sheathing sagging between the trusses?

• Why is granule loss a problem for an asphalt shingle roof? 

• What are the mistakes to avoid when doing attic improvements?

• What causes roof shingles to curl up at corners?  

• What causes shingles to buckle along a line on the roof?

• Is an attic required to have a light by the building code? 

• How can I inspect my roof for hurricane damage?

• Why is premature curl of roof shingles a problem?

• How can I tell if a roof has more than one layer of shingles? 

• What are the common problems with attic insulation? 

• What is the life expectancy of an asbestos cement shingle roof? 

• What's the average lifespan of a roof?

• Why is it a mistake to replace a roof and not replace its flashings? 

• Why is there no attic access hatch in the house?

• If my roof is not leaking, why does it need to be replaced?

• How can I be sure my roofing contractor got a permit?

• How many layers of roofing are allowed on a home? 

• What are the dark lines running parallel to shingles on my roof?

• Can metal roofing be used on a low slope/pitch roof? 

• How can I make my roof last longer?  

• What are the warning signs of a dangerous attic pull-down ladder?

• How can I find out the age of a roof? 

• Should I buy a house that needs a new roof?

• Should I buy a house with an old roof? 

• What are those metal boxes on the roof?

• What does "lack of tab adhesion" in an asphalt shingle roof mean?

• Why do roof edges start leaking?

• Why do my dormer windows leak? 

• What does a home inspector look for when examining a roof? 

• Do stains on the ceiling mean the roof is leaking?

• How can I tell if the house needs a new roof?  

• Why does my homeowner's insurance want a roof inspection?

• What are the hazards to avoid when going into an attic? 

     Visit our ROOF AND ATTIC page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.