You’ve just finished a roof repair project with Enduris™ Roof Coatings, when you notice blisters appearing on the surface you’ve just coated!

What do you do?

Start again? Cut them? Re-coat them? Do nothing?

Blisters might look unsightly, but they are rarely a sign of a serious problem. In this post, we look at blisters, why they form, and what to do about them.

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Blisters – Setting the Scene

If you’re coating a roof, you’re likely to come across blisters regularly – they happen all the time.

Every roofer knows just how damaged a roofing surface can become. Roofing substrates are subject to a lot of adversity, as weathering, moisture, dirt and grime build up over years and years can significantly impact the performance of a roof.

Putting a roof coating on any substrate completely changes the dynamics of the surface and the building.

The job of a roof coating is to restore the performance of this damaged surface, to prevent leaks, and to help protect the building for years to come. It requires the creation of a durable, seamless membrane that is breathable, waterproof, and permanently flexible.

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What Causes Blistering on Roofs

Most blisters are caused by the same thing - moisture.

When you coat a roof, you seal moisture inside the substrate. It is now trapped underneath the coating, with nowhere to go. When the roof heats up, due to the sun or internal building heat, this moisture evaporates and becomes water vapor that expands by up to 1300x its volume.

As this hot vapor rises, it comes up against the newly applied roof coating, applying significant pressure. When this pressure becomes too much, it causes small sections of the coating to become unadhered, and a blister is formed.

To check a blister, lightly press on it with your foot. If the blister is hard and no air releases or water squirts out, you have a blister with vapor in it.

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Blisters – How to fix roof blisters

So, what do you need to do about these blisters? The answer, in most cases, is nothing!

Most blisters are a cosmetic issue. If the coating around a blister remains adhered to the substrate, blistering should not impact the performance of the roof. When using a product that allows moisture to escape, as does Enduris roof coating, the problem is likely to correct itself over time.

Never cut a blister.

Piercing or cutting a blister ruins the seamless finish of the coating, creating a natural weak point in the restoration. It increases the likelihood that the coating will become loose, and may reduce both the performance of the roof and its lifespan.

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How to Minimize Blisters

One of the easiest ways to reduce the impact of roof blistering is to use a high-quality product with a good perm rating, such as Enduris roof coating.

With a permeance rating of 9.3perms, Enduris 3500 roof coating allows the built-up vapor and trapped air to vent out, flattening the blister.

Another way to minimize blistering is to utilize a cool roof coating, such as Enduris coating in white. Using a white colored coating will help to keep roof temperatures down. This will reduce water vapor development, decreasing the incidence and severity of blistering.

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Roof Blistering - Key Takeaways

The key messages when it comes to coating blisters are:

• Blisters are common
• The vast majority of blisters are caused by trapped moisture
• They are usually nothing to worry about
• Most blisters are a cosmetic, rather than a performance issue
• Most blisters will vent out over time with Enduris roof coating
• NEVER CUT A BLISTER

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Repair and Protect - with Enduris Roof Coating

For roof restoration and new roofing projects, Enduris Roof Coatings offer a complete silicone coating system that can significantly extend your roof life expectancy.

Applying Enduris roof coating couldn’t be easier – and a single coat can provide up to 20 years of added protection**. This 100% silicone solution requires no mixing, and no primers, and is available in a range of standard and custom colors to suit virtually any project.

Applied directly to a variety of substrates, including TPO, PVC, EPDM, Mod-Bit, metal and SPF, with spray, roller or brush – it creates a waterproof, resilient and seamless barrier against leaks, to extend roof life and reduce the need for maintenance.

We are here to help. For additional information about Enduris roof coatings, visit us here or contact your local representative today.

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