When is the last time you gave some serious thought to your roofing underlayment? Chances are you give a lot more thought to your underwear. What kind of underlayment you need for your roof is typically a decision you make only once in a lifetime, unless you are a buffalo roofer. That’s how often you will typically need to reroof you home and that’s the only time you will likely think about it, because once the roof is on, the underlayment is out of sight.
Even as recently as 20 years ago, consideration of underlayment in a residential roofing project wasn’t a high priority. Some roofs didn’t even receive underlayment. Today that has changed due to many state and local building codes, and the advancement in underlayment technology. Underlayment is one of the most critical components on a residential roof and should be thoughtfully selected, as it can impact the quality and longevity of a new or replacement roof.
What Is Roofing Underlayment?
Roofing underlayment is a material that installs on top of the roof deck. Most roof decks are plywood’s of various grades; older homes may have tongue and groove planking. It is a protective barrier that is sandwiched between deck and shingles. It is traditionally made of felt and saturated with asphalt to facilitate a bond with the asphalt shingles. This material is often called roofing felt and comes in a variety of qualities. The most common grades are 15# (pound) and 30# (pound).
New synthetic underlayment materials have recently been introduced known as “synthetic felt”. These are synthetic polymers or similar materials, which add a higher performance barrier to the roof in specific applications, extreme weather conditions would be one example. Also, it is highly recommended to use a synthetic underlayment for metal roofs or any shingles expecting to exceed 40 years in life.
Improvements have also been made to the “traditional” asphalt roofing felts. The recent introduction of asphalt coated glass reinforced felt underlayment has a lot to be desired. Manufacturers of this improved roofing felt equate this as better than a 30# felt because of its strength and toughness. Roofer like this new product because it lays flatter and comes in larger 4 square rolls vs. the 2 square 30# rolls.
Many manufactures will specify what types of underlayment’s are necessary to validate and maintain warranty conditions of their shingles. It’s important to communicate with your roofing contractor to understand the requirements of these systems.
One of the lesser-known benefits of underlayment is aesthetics. This may be especially important with traditional three-tab shingles, which have a thinner profile than architectural shingles. Underlayment’s reduce the effects of any uneven sections of your deck, mitigating waves and bumps. A good looking roof adds value to your home.