Flat roofs are traditionally found wherever the climate is hot and dry and rainfall is not significant. The term flat roof is a bit misleading, as even this type of roofing system must have some gradient so water will not accumulate on it. But from an aesthetic standpoint, the look is radically different from that of a traditional pitched roof found on the vast majority of homes worldwide. A flat roof is associated with southwestern and pueblo style homes and more modern architecture, such as art-deco and the modernist movement.
The use of flat roofs in areas where rain and snow are significant has grown in the past decades as new materials have been developed that make the use of a flat roof more practical in any climate. In excessively wet weather, the low gradient of the roof cannot keep up with the flow and results in flooding. Cold weather in particular takes its toll on older flat roof systems. Even with a slight gradient to shed water, a flat roof is particularly susceptible to ice accumulation. The ice formation blocks water flow during thawing leading to pooling and moisture seepage beneath the roof surface. New flat roof technology and materials offer better seals making the roof far more waterproof than previous systems.
Aside from aesthetics, a well installed flat roof has other advantages over a sloping roof system. One advantage is the ease of construction, which results in much lower costs. A flat roof features no complicated angles and or compound cuts to make, so work is quicker and less material is needed. Inspection and repair is also much easier. No scaffolding or special harnesses are required as in a sloped roof.
Space utilization is also better with a flat roof system. A pitched roof has a large open space under the roof which can be less energy efficient. The level area of a flat roof can also be put to use for other needs, such as HVAC equipment, or living space. It can also make designing according to local building height and set-back requirements easier to adhere to as there is no high roof peak to consider.