Last time, we looked at what roof underlayment is and why you need it as part of your roof installation. Like the proper sheets on a bed, underlayment can make a big difference in the performance of your roof.

Ok. So now you know to make sure that roofing felt is included in your roof replacement, but it sounds like it’s pretty standard. What else do you need to know?

Well, thanks for asking!

While you might get a few hours of sleep with any old bed sheets, with a little bit of thought and effort your sheets could make restful sleep a lot easier. The same goes for underlayment. Let’s explore your options.

A relatively new development in the roofing industry, synthetic felt has been a game changer. While there are hundreds of options in this category with many different features, they all essentially attain the same outcome: better safety, durability and protection. Most have a polyurethane base with some kind of top layer to add grip for crews to walk on.

• • Pros:
    • Breathable
    • Significantly better water repellant
    • Very tough and doesn’t tear easily
    • Light weight 
    • Easy to install
  • Cons:
    • Prices could be only slightly more expensive than 15# felt or as much as triple the cost per square

This is the traditional underlayment that has been used for many years. It is a layer of natural materials such as wood cellulose covered with a coating of protective asphalt known as bitumen. 

• • Pros:
    • Cheapest option
    • Breathable
  • Cons:
    • Tears easily so it isn’t as safe to walk on
    • Tears easily so it may blow away with the shingles in a storm
    • Absorbs water

This is essentially the same as 15# felt. It is just thicker and is typically installed on steeper roofs. It won’t tear as easily as 15# felt so it is a little bit safer to walk on.

• • Pros:
    • Breathable
    • Repels water better than 15# felt
    • Doesn’t tear as easily as 15# felt
  • Cons:
    • More expensive
    • Absorbs water