How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
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Why are most house roofs slanted instead of flat?
Monday, June 25, 2018
Flat and low-slope roofs were briefly popular during the post-war decade of the 1950s and into the early 1960s, largely due to the influence of the spare, angular style of the modern architecture movement. The futuristic designs of architect-designed homes for wealthy clients during the era, like in the concept rendering shown below, percolated down to more modest versions in model homes of housing developments around Florida.
Here’s two interpretations of that design concept, scaled down for housing developments in Gainesville, Florida.
And an even more basic example with a flat roof in Gulfport, Florida.
There are several reasons, besides the fact that flat and low slope roofs went of out style, that they are rarely used for newer homes. Here’s our list:
- Air conditioning and heating ducts are usually installed in the attic, but no space for them in a flat or low-slope roof home. Ducts have to be installed in dropped soffits, usually in hallways, around the home. This severely limits where air conditioning vents (registers) can be located.
- The space required for ceiling insulation is limited or non-existent. Energy costs were cheaper back then, and it was not so important, but complying with today’s energy code standards requires plenty of room for insulation below the roof.
- Homes with a sloped roof can use shingles and other roofing materials that overlap downhill to make them water-resistant. They depend on the rain water flowing downward to be effective. Flat roofs have to endure standing water, called ponding by roofers, and must be sealed watertight. They are more expensive to install and leak-prone as they age. Here’s an example of ponding on a flat roof below.
- A sloped roof, like in the photo below, makes any house look taller and look more impressive.
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To learn more about roofs and attics, see these other blog posts:
Architectural renderng at top of page by architect Ralph Rapson of “Greenbelt House,” part of the Case Study House program, initiated by Arts & Architecture magazine, 1945
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