Flat roofs are a common architecture feature in homes of all styles. From a simple lean-to to a multi-million dollar mansion a flat roof is attractive and functional. Flat roofs are easier to install, cost less, and have fewer maintenance problems.
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No Flat Roofs
Technically, very few roofs are actually flat. The greatest problem with a completely flat roof is drainage. Water puddles on the roof, which increases the risk of a leak developing. Snow stays on a flat roof longer because it has no way to slide off.
The flat roof look is achieved with what is called a low-slope roof. According to the American Society for Testing and Materials Standard E 1918-97, a low-slope roof has a maximum slope of 2 inches "rise" for 12 inches "run."
Example of Rise
A low-slope roof that is 30 feet long would be 60 inches taller at the peak than the bottom edge of the roof. This allows proper drainage.
Hiring a Contractor
Flat roofs are more complex for waterproofing. Carefully check a builder's credentials, understanding of flat roof design and experience installing them.