Which roofing underlayment is best for a metal roof?

Answered by Brett Kulina ~ October 22, 2012 ~ Comments

I am putting a new metal roof on my house, replacing old shingles. I have stripped off the shingles and the old tar paper from the plywood. Now what should I use under the metal?

Brett Kulina

It used to be that 30 lb. roof felt, also known as tar paper, was the standard underlayment for most new roofs, as it is easy to work with, somewhat durable, and moderately inexpensive. Of course, times have changed (for the better) and now there are several roofing underlayment products available that are far superior to standard roofing felt.

Grace Ice and Water Shield is a self adhesive underlayment that is installed just like traditional tar paper, but Ice and Water is a much better product. It is less likely to ripple after installation, because its adhesive properties help it to lay flat, and its rubberized asphalt layer actually seals around nail and screw holes. Ice and Water rolls out easily and its rough surface is slip resistant. Keep in mind that there are 2 types of Ice and Water underlayment, one is for use under shingles, while the other is a high temperature product that is specifically designed for use under metal roofing panels.

Another option is Dupont Roofliner, which is both more durable and lighter weight than asphalt roofing felt. Dupont Roofliner is similar in feel and look to the compnay's Tyvek building wrap, which has been around for years and is one of the standard weatherization products in the industry, but remember that the two products are not interchangeable.

Whichever product you choose, keep in mind that the slope of your roof, as well as other site specific conditions, may dictate which product is ultimately best for your project. Although both Ice and Water Shield and Dupont Roofliner are more expensive than traditional asphalt roofing felt, I feel that the improved durability is well worth the higher cost. Prior to installing either product under your home's new metal roof, make sure to read and understand all of the manufacturer's installation instructions. This way your new roof will be long lasting and worry free.

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