Commercial Roof Puncture Guide

A major cause of leaks on flat commercial roofs is due to punctures. Knowing the causes can help prevent punctures, but you also must know how to spot and repair them.


There are a variety of issues that can cause punctures on flat commercial roofs. The most common cause is traffic on the roof. Most commercial buildings have major appliances, like HVAC systems, on the roof. These require periodic maintenance. Walking in the wrong area or dropping a tool can puncture or weaken the roof membrane. Even if not punctured, the weakened membrane is more likely to develop a hole later.

Weather conditions are another common cause of punctures. UV light and sun exposure can weaken a membrane over time, causing hole development. Punctures can also occur from impact damage, such as from blowing branches or other debris. Even components on the roof, such as a vent cover, can cause a puncture if they become dislodged during a high wind event.


Punctures are quite obvious from above in most cases, so regular inspections should be a scheduled task for your building maintenance crew. Surveying the roof will indicate puncture locations, particularly on membrane roofs. The membrane may appear wrinkled or there may be a visible hole or slit in it. Water often pools around punctures, as well, which can make them easier to locate.

Inside the building the most obvious symptom that a puncture has occurred will be water leaks. Keep in mind that the location of leaking water doesn't necessarily indicate the location of the puncture in the roof. Water can seep through the ceiling and travel quite far before it finds the easiest path to leak through and into the building proper. Consider leaks to only be diagnostic of the existence of a puncture, not its location.

Repair Options

Fortunately, a puncture doesn't usually mean that you need to put a whole new roof on the building. Most types of flat roofs can be effectively patched. Built-up roofing, also known as asphalt roofing, is repaired with a hot asphalt patch over the puncture. A reinforcing membrane may also be applied and sealed in place with tar to prevent leaks around the patch.

For a membrane roof, the damaged section is cut out and the edges are sealed down to the subroofing. A membrane patch is then adhered fully over the damage. In many cases, a protective coating is then applied to further prevent leaks from occurring at the location.

Contact a commercial roof contractor in your area if you suspect puncture damage on the roof.