The changing of the seasons and the accompanying shifts in temperature and humidity can result in blisters on your roof. Roof blisters appear as raised areas or bumps over voids—empty spaces between roofing layers or underneath roof coating. They can also occur above places where adhesion has been lost, such as if the roof ply or roof coating film has lifted from the underlying surface.
On flat roofs, blisters appear as small bubble-like protrusions, thin and long raised lumps, or large, spongy areas. While small blisters are generally harmless, ones of a significant size must be addressed to prevent further damage to your roofing system.
What Causes Roof Blisters?
Roof blisters can occur on any type of conventional, low-slope, and flat roofing system, but they’re most common in membrane systems and built-up roofs (BUR). Errors in the manufacturing process of roofing materials can create voids that result in blisters.
Moisture and air can become trapped in voids between roofing plies or between the substrate and the membrane. As temperatures rise, the heat causes the water vapor to expand, which in turn causes roof blisters.
If the blister is punctured, it could expose the underlying surface to the elements. This could result in water getting inside the roofing system and even into your property’s interior, causing mold growth and water damage.
Preventing Roof Blisters
Improper installation is one of the main causes of roof blisters, it’s critical that you hire a skilled and experienced contractor to install or replace your roof. The ideal contractor will take the necessary steps to prevent the loss of adhesion that results in blisters, and that the roofing area is clean and dry before and during installation.
If you already have a roofing system installed, here are some other ways you can prevent blisters from forming:
Keep the Roof Dry & Clean
Regularly clear away debris, such as leaves and twigs, from your roof to prevent them from clogging drains and gutters and causing water to pool on your roof. If your property is located close to trees, consider trimming their foliage.
Limit Foot Traffic
Stepping on a roof blister can cause it to pop. To avoid this, consider limiting access to your flat roof and allow only those who need to be there, such as roofing contractors and maintenance crew.
Schedule Regular Roofing Inspections
According to GAF, a commercial roof should be inspected at least once a year. Annual inspections can help alert you to blisters and other roofing issues before they turn into major problems that require extensive repair.
When to Call a Contractor for Roof Blisters
It can be hard to tell by sight alone whether a roof blister is harmless or if it needs to be repaired. However, keep an eye out for the following types of blisters, as these need to be addressed right away by a qualified contractor:
- Roof blisters in seams
- Blisters that have broken open
- Blisters with cracking around it
- Blisters in high-traffic areas
- Very large blisters
- Widespread blister formation on your roof
The Final Word
Your commercial roofing system is a significant investment that needs to be protected. Regular inspections, scheduled maintenance, and timely repairs can help prevent roof blisters from further damaging your roofing system and the structure it protects.