History

• Evidence of flat-roof construction occurs as early as the Minoan period, around 2000 B.C., when large timbers braced across small stone structures and covered with wood or thatching provided shelter from the elements. Today, flat roofs are popular in the construction of Southwestern-style homes and commercial buildings.
  
  

Benefits

• Flat roofs provide a substantial warmth factor during the cold season as the flat surface attracts sunshine and transfers it to the dwelling below. In addition, as in commercial buildings, high rises or apartment complexes, a flat roof often doubles as patio space and offers an alternate exit from tall buildings. Rooftop gardens and even rooftop swimming pools are possible with a flat roof. Additionally, because constructing a flat roof takes less material and labor, the original cost is less than that of a gable roof.
  
  

Types

• Flat roofs built between 1940 and 1985 were likely to have hot tar or asphalt as a covering and a sealant over a wood-frame structure. Although this method is still in use today, new techniques using gel membranes and sheets of polyvinyl chloride (PVC) provide more protection from water leakage. Bitumen-type roofs are inexpensive and feature pebble-covered tar paper, rolled out in strips that meld together when the temperature on the surface rises above 110 degrees .
  
  

Considerations

• Flat roofs require constant maintenance. The average lifespan of a rolled-tar or bitumen flat roof is 10 years if it is well-maintained. Unless the roof is structurally designed to hold weight, every footstep creates undue pressure that may result in a crack and a future leak. Gel membranes, used on commercial high-rise roofs, are cost-prohibitive for the average homeowner.
  
  

Potential

• Flat roofs can help you reduce energy costs in the winter, but the reverse is true in the summer months, as the sun beats down on the roof and the only place for the heat to go is inside the dwelling. For this reason, most homes with flat roofs fare better in temperate, arid climates. Indigenous natives of the southwestern United States often poured water on top of their flat roofs in the hot summer to cool them down.