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Blistering Roof Shingles: “Mumps” Causes

Blistering Roof Shingles

Blistering roof shingles can be common on new roofs and requires roof replacement. Shingles that have this condition, sometimes called “mumps”, can significantly lower the life of the roof and cause early roof leaks.

What Causes Blistering Roof Shingles?

Blistering occurs when water is left on asphalt shingles as the granules (or top layer) is applied. Once applied, the water evaporates and “blisters” or pops granules and some asphalt off of the shingle.

Blistering typically happens within the first year of initial install. Furthermore, blistering should not be confused with hail damage that is caused by an impact.

Check out another image of this shingle manufacturer defect:

Blistering shingles - manufacturer defect

What To Do If You Have Blistering Roof Shingles

If you discover some shingles appearing to blister, you should notify your roof installer or manufacturer immediately. In most cases, blistering can be found right after the initial install and the shingle manufacturer will pay for a reinstall.

Be careful of voiding warranties (incorrect installs/repairs) and be sure to keep all documentation from the shingle type to the contractors that installed it.

This is why it is so important to have a credible roofing company that will install your shingles according to manufacturer specifications.

Need Some Help?

Home inspectors are trained to spot shingle defects and can assist you in this process. Be sure to contact us or another credible company for help if you need it.

InterNACHI has more information available for home inspectors or homeowners on spotting the differences between types of shingle damages.

If you have more questions, be sure to leave a comment below!