What is Underlayment and Do I need It?

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What is Underlayment and Do I need It?

June 20, 2018 Blog 0

What is Underlayment?

Underlayment is a water proofing layer of felt.  It is installed between the plywood and the shingles. It is considered the waterproofing barrier that keeps the moisture from penetrating the layer of shingles and rotting the roof deck.

Do I need it?


If any water gets under the shingles due to shingle damage moss build up or ice dams, the underlayment is extra protection for your roof deck.

Even if your roof is in good shape, wind storms and other extreme weather can loosen or remove shingles from the roof.

Let’s say there is a storm and your shingles become loose or blow off.  And after the storm, there continues to be bad weather for a few weeks. If you have a good underlayment, your home should be protected until you are able to get it repaired.  However, if you do not have underlayment, you can begin to get roof damage immediately.

With the correct underlayment, the roof technician only needs to replace the shingles.  This is a simple and fairly inexpensive repair.

Without an underlayment, your repair is massive.  It now includes removing large portions of surrounding shingles and replacing sheets of plywood. Even worse it can include replacing framing or trusses depending on the extensiveness of the damage.

Bottom Line

The felt underlayment is a second layer of protection.  It is absolutely necessary for the effectiveness of your roof system.


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