In general, flat roofs offer plenty of advantages for homes designed with such a capability. Flat roofs are cost effective, easily accessible, and, depending on the material used, energy-efficient. They also offer the ability to utilize the space atop the house for other functions, such as placement for air conditioning units or solar panels.
However, flat roofs are far from perfect. In exchange for this architectural style and other benefits, you get a bevy of concerns that wouldn't be a problem with a traditional shingled roof. To get the most out of your flat roof, these are seven common problems to bear in mind:
1. Ponding water
Most flat roofs aren’t truly flat—they have just enough pitch (or slope) for water drainage. However, there isn’t much margin for error. If the flat roof is damaged in any way (more on this later), or if ice is damming on it, water can begin gathering into small ponds and lead to more serious problems, including systemic leaks inside the house, moss and algae growth, and additional damage to the roofing system.
The lack of a slope allows leaves, branches, and other debris to collect more easily on a flat roof and block drainage. Moreover, a big uncleared pile of leaves holds in moisture that can freeze, thaw, and refreeze throughout the winter. This cycle will wreak havoc on the roof underneath.
Yes, “alligatoring” is a real term; it refers to a flat roof that has begun to crack and bubble, resembling the skin of an alligator. Usually, sun exposure over time is the cause of this problem—and you can’t quite turn off the sun. If left untreated, an alligatored flat roof can lead to additional cracks, leaks inside the home, and a complete failure of the roofing system.
Houses settle and shift over time. As a result, so does the roofing membrane between a house and the roofing material. Since a flat roof’s membrane is one continuous sheet, this shifting can cause it to buckle. A poorly installed flat roof can also contribute to buckling, which can also lead to greater problems, and possibly a roof replacement sooner rather than later.
Roofs must be able to withstand the elements, especially wind. If a shingle or two is blown off a conventional roof, though this is not ideal, the rest of the shingles are designed to hold in all but the windiest conditions. Since flat roofs are one sheet of material, a little wind damage can turn into a lot of wind damage with just a few additional gusts. The whole roof can fail and necessitate immediate replacement.
Ponding water, alligatoring, buckling, and the natural elements can all contribute to a leaking flat roof. However, leaks can still develop without these issues. For example, damaged flashing can cause leaks as easily on a flat roof as on a sloped roof. Poor installation, substandard materials, or simple age can also factor into flat roof leaks.
7. Shorter lifespan
After expert installation, a flat roof should last a minimum of 15 years, and perhaps as many as 30 years. In general, that is a shorter lifespan than an asphalt shingle roof, and far less time than cedar and metal roofs. New homeowners of existing homes, unsure of their flat roof's age, should anticipate that a roof replacement may not be far into the future.
These flat roofing problems are valid concerns, but they shouldn’t sour homeowners on the benefits offered by a flat roof. Extending the life of the flat roof only requires the homeowner's extra vigilance and a commitment to scheduling regular maintenance.
What flat roofing problems have you encountered with your home?