Your Crash Course in Underlayments

By Cass Jacoby. 

As a homeowner, you will need to make a lot of decisions about your roof, like choosing the right underlayment. Learn everything you need to know to make the right choice for your home. 

In Season 1, Episode 2 of the AskARoofer podcast Alice and Megan sit down with Dominic Favazza of GCP Applied Technologies to talk underlayments. For many homeowners and non-roofers, knowing what an underlayment does or why it is important typically won't come up until it’s time to replace your roof. You won’t want to miss this crash course that tells you everything you need to know about underlayments and answers all your questions on this vital piece of your roof. 

So, what is an underlayment? “Just to break it down in its simplest form, underlayment is what lies between the shingles and the roof deck,” says Dominic. “So it is the layer that sits directly on your roof deck, which is typically going to be OSB or plywood, and it provides a secondary layer of protection against the elements. Stuff like rain, snow, ice, wind. It just adds an additional layer of protection from those elements entering your home via the roof.” 

Sounds pretty straightforward, right? Well, there are many elements to consider when choosing the right underlayment and a myriad of choices. “There's a bunch of different factors that come into play for a homeowner determining what is their best course of action for waterproofing the home,” says Dominic. “So what I always like to say is to think about your roof, not as the shingles that you're putting on, but thinking about your roof as a system. And that system, it differs depending on where you live. So because of that, you need to have the proper underlayment for those types of weather.” 

When it comes to choosing an underlayment, you can think of them in two categories: the mechanically fastened underlayments, often made of synthentics or tar paper, and self-adherent underlayments. According to Dominic, if you get a lot of hurricane winds or wind driven rains, for example, you might want to choose a self-adhering underlayment to ensure heavier coverage.  

With so many underlayments to choose from and numerous factors that play into how well an underlayement will work for your home, Dominic recommends educating yourself on underlayments so you have a baseline understanding of what you are looking for.  

“Information is everyone's best friend. Educating yourself is the most important thing that a homeowner can do,” says Dominic “If you just have a little bit of baseline knowledge, it'll really help you in the long run, just knowing what you want and what that contractor is going to provide you.” 

Listen to the podcast to learn more about why underlayments are important to your roof system and how to make the best possible choice for your home. 

Have a question? AskARoofer.   

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About Cass  

Cass works as a reporter/writer for RoofersCoffeeShop, MetalCoffeeShop AskARoofer and MetalCoffeeShop. When she isn’t writing about roofs, she is putting her Master degree to work writing about movies and dancing with her plants.