The Oft-Maligned Flat Roof

Flat roofs: we’ve seen them everywhere; on commercial buildings and private homes, on factories, hotels and airport terminals. People think that flat roofs always leak, but that reputation is undeserved when the roof is built properly. Flat roofs can have many advantages, including increased interior ceiling height and reduced cost. They can easily accommodate walking decks and solar equipment, and can be useful components of building additions and new homes–as long as they’re placed in the right spot and built well.
In reality there is no such thing as a flat roof. All roofs slope in one direction or another, because they need to shed or drain water. The building code mandates a slope on even the smallest of roofs. A roof that is truly flat will not drain or remove water properly, so even if the code did not require a slope, a good contractor (and architect) would still design it in. A better term for such a roof is low-slope roof. Nearly flat, but not quite.

Low-slope roofs have a leaky reputation because these roofs can be built or repaired very cheaply– and this has led to large numbers of badly-constructed, unreliable roofs throughout Los Angeles. Consider that the biggest building expense is labor, and that cheap low-slope roofs can be built or repaired by relatively low-skilled labor. This means that many inexpensive low-slope roofs are also very poorly built or repaired (although this is not necessarily or always the case), and often develop leaks. Low-slope roofs that are designed and built to a high standard, however, are very reliable, and remain so for many years. Although they are more expensive than cheaply-built roofs, they are often less expensive than conventional pitched roofs, and sometimes offer many advantages over them.

It is true that the architect must pay a great deal of attention to technical details. And the builder has to make sure that the details of the roof’s construction are expertly carried out. If the roof is also intended as a place for people to walk, extra attention is needed with the roof’s design, material specifications and care in construction to make sure that the roof is not damaged with use. A finicky roofing contractor is a good one to have with low-slope roofs. A good low-slope roof will provide trouble-free service for a very long time.

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Chautauqua house, Pacific Palisades

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Chautauqua house, Pacific Palisades

Why use a low-slope roof? In many cases, these roofs provide a variety of important services beyond keeping water out of the house. A low-slope roof can easily accommodate solar panels and heating/air-conditioning equipment. It can be a good place for a deck, and especially so when a person can step directly from a second-floor bedroom out to a deck with a view.

Even when built to a high standard, low-slope roofs can still be less expensive to build than conventional sloped roofs because the construction is often simpler (although there are exceptions to this as well). And such roofs can often provide more ceiling height indoors without violating zoning-code height restrictions on the building. They can easily be integrated in a house’s design (attending to the appearance of the exposed edge of the roof is critical), and may even be concealed by extending the house’s outside walls up above the roof, forming parapets that hide rooftop equipment from view.