Roofs are not the most exciting of architectural elements, but the argument could be made that they are, in fact, the most important part of the building. It’s no coincidence that we say we’re grateful for ‘a roof over our heads’, they protect us from rain, sun and snow.
And since roofs take such good care of us, we need to take good care of them!
Among roofs, “flat” roofs are rather unappreciated. You usually can’t even see them from the ground! But they are common around town – big box stores, hospitals, restaurants, and even SOA’s own office, have flat, membrane roofs. “Flat” is a misnomer, because all roofs must have some slope in order to drain. Typically, we design flat roofs to slop about 1/4″ per foot. Flat roofs are easy to navigate, maintain, and relatively less costly to construct.
Regular inspection is important. Flat roofs slope to drains, usually toward the center of the roof. Generally, these drains have a type of perforated metal cap that prevent large chunks of debris from entering the drain. The issue here is that on occasion, the perforated metal cap can become clogged and not allow water to drain off of the roof.
The first indication that a drain is clogged is when water is spilling out a lamb’s tongue drain on an exterior wall. Normally, no water should be draining here.The lamb’s tongue is piped to an overflow drain that is usually located slightly uphill from the primary drain. When the primary drain is clogged, and water backs up, then the overflow drain and lamb’s tongue are activated. Often scraping away the debris build-up is enough to get the primary drain flowing again.
The physical outer cover of a flat roof consists of sheets of material that overlap at the seams and are chemically sealed together. The bond between the sheets should be strong enough to hold water. However, these can be a point of roofing failure. Splits in these areas aren’t common, but special attention has to be paid, especially during freeze-thaw cycles. If water gets between the sheets at the seam and freezes (thereby expanding), it can tear the roofing and when it thaws, leak into the building. Commonly, this will first occur when the roof is new, due to poor workmanship. As time goes on, however, UV rays from the sun can do damage to these parts of the roof, too.
Another, more obvious thing to look for are holes. Although the roofing material is durable, crazy things can end up on roofs that puncture holes in the material. Gaping holes are easy to identify. But, there are more subtle injuries to a roof that can be harder to identify. Sometimes birds can bring debris to a roof (we recently found a turtle shell on our roof) or a roofing installer might accidentally drop a screwdriver or utility knife. These small punctures may take years to manifest as leaks. Anything sharp or abrasive can be detrimental to a roof. Which is why we often specify protective walk pads from the roof entry point to frequently accessed areas, like around mechanical equipment.
These considerations are just the tip of the iceberg. On every project, SOA thoughfully helps evaluate decisions like: which type of membrane roof is appropriate (EPDM, TPO)? Which manufacturer has the best warranty? What kind of experience should an installer have? How should the roof membrane meet the parapet wall?