“Different types of roofing underlayment”

    The roof underlayment or most commonly known as “felt paper” is the first layer of waterproofing materials that goes before the shingles or roofing materials. It is mainly a roll of paper or fiberglass saturated with asphalt and other waterproofing materials.



     There are many new types of underlayment and it can be difficult to know which underlayment to choose. The most common as we said before is the regular felt paper. The felt paper is typically used in most roofing jobs as a release between the two materials; wood and asphalt. Roofers started using felt years ago on roofs to help prevent the damaged caused from sap leaking out of the wood and breaking down the back of the asphalt shingles and causing them to deteriorate. That really is not a problem anymore because builders now use plywood. Another big reason why they started using the felt was because the outside heat and the heat of the attic combined would practically melt the asphalt shingles to the wood. So it made it easier to have that extra layer of felt, for the next roofer when they would do the tear off and install the next roof.  In many occasions felt also would work as a lightweight protection against any damage on a stormy day. If a shingle or a tile breaks or blows off during a storm, the roof would be protected by the layer of felt paper. It will have some protection that will resist the driving rain temporally and give the homeowner some time for to get that damaged section of the roof repaired.



    Now some of the different manufacturers are offering all of these new types of underlayment’s, from synthetic to organic, and even those 2 combined (don’t ask). In reality some of these new products are extremely effective, they will last being exposed to the elements for up to 6 months. They even have anti-slip technology to protect the people who install the roof. Some of them also promise you that they will help to keep moisture out and that they would help your roof “breathe” better and last longer as a result of it.


    One thing to consider is this, with most roofing jobs the felt will be exposed about 1 to 2 hours and after that you would never see it again for another 30 years. The felt will be completely covered with the shingles with hundreds and even thousands or little roofing nail holes (that’s plenty of ventilation to “breathe”). If you have a good shingle installation any type of underlayment will suffice. A $20 roll of felt would perform the same as a $200 synthetic underlayment. Many people fall for the sales pitch that some companies offer with these types of underlayment’s to justify their high price but in my humble opinion it is  just another up-sale. In reality most reputable roofing companies install a type of membrane or leak barrier that fully adheres to the plywood on the areas of the roof that would be a possible leak (valleys, dormers, chimneys, skylights, pipe vents,etc) for extra protection. I know we always do, and that’s because we do not like leaks on roofs we installed. Specially when they could’ve been prevented.

    Going back to the synthetic underlayments, I do not deny that they are worth the price because they are actually extremely resistant, thick and nice to work with. But since they won’t be exposed for long periods of time it’s really up to the homeowner to choose if they would like that fine layer of underlayment under their shingles.










When choosing a type of underlayment always try to go with the manufactures felt. It is always smart to go with the same brand of your roofing materials because in case of a warranty claim you would have a whole roofing system installed and not a mix of different brands.

Thanks for reading this.

Jon Montes

¡Soli Deo Gloria!