No matter where in the country your commercial building is located, roof leaks are a possibility. And water in your building can originate from several potential sources, so it’s important to check all of them when you conduct roof inspections to make sure your building contents and occupants stay high and dry.
Virtually all commercial roofs have penetrations, such as HVAC curbs, drains, vent stacks, and skylights. Restaurants typically have a lot of penetrations, whereas warehouses and similar facilities may have relatively fewer. Penetrations involve a “change in plane” from the horizontal roof surface to the vertical aspect of the (e.g.) curb. The roof material connecting the horizontal and the vertical is called a flashing, and it’s the most leak-prone roofing element for a couple reasons. First, many roofing systems require that flashings be constructed and assembled on the roof itself. This operation creates the possibility of human error affecting the quality and long-term watertight effectiveness of the flashing. Some manufacturers have addressed this problem by making customized prefabricated flashings in the factory, reducing the probability of error on the rooftop. The second reason is that flashings can be under more stress than other sections of the roof because of normal expansion and contraction.
Roof membrane is terminated around the perimeter of buildings, using a variety of methods. Coping cap, drip edge, gravel stop, compression metal and other systems can be used, depending on the specific situation. The roof’s perimeter is under a lot of stress, as it bears the brunt of wind forces, and the taller the building, the greater the force. The edge fastening details and the roof membrane attachment on the deck around the perimeter work together to keep the edge watertight. When your new roofing system is installed, make sure that the edge termination is sufficient to withstand the wind and driving rain that you can expect on those parts of the building. Also make sure that you thoroughly inspect the perimeter of your roof after severe weather events to make sure that your edge system is holding fast.
Although not specifically a roof leak problem, condensation is often attributable to roofing issues and is created when the warm, moist air inside the building contacts a cold roofing surface or when cold air leaks in through the building exterior. Moisture can form and eventually find its way into the interior because of a missing or inadequate vapor barrier on ceilings or walls, or from inadequate insulation or ventilation. A relatively easy way to deal with moisture issues is to improve the air flow in the cold space by adding venting or even fans. Building owners could also add insulation or a better vapor barrier, but that may be more involved once the roofing system is in place.
The best defense against water penetration is ensuring that these critical areas are inspected regularly and dealt with promptly.