The covering on your roof, whether it is asphalt shingles, metal, wood shake or any other material, is a water shedding device only. Roof coverings are not waterproof! Heavy winds can drive rain up underneath shingles. Ice dams can also cause water to back up on the roof and seep beneath the covering. Storms can also cause damage to the primary roof covering, such as from flying debris or hail, enabling water to get to the deck and into the building.
The roofing underlayment serves a couple of functions. First, it provides a temporary water shedding covering for the roof while the new shingles are being installed. After the primary roofing is installed, the underlayment is then the second line of defense protecting the home from water infiltration. A good roofing underlayment should perform this function for the life of the primary roof covering.
For many years, asphalt saturated felt was the choice of roofers for roofing underlayment. A lot of them still use it today mainly because it is the cheapest thing to do. Today’s felts are not what they used to be 10 or 15 years ago. They have much less asphalt content today then they ever had. Asphalt has increased in price over the past 10 years and the felt manufacturers cut back the amount of asphalt in the felts to keep prices down. Though the price remained low, the quality decreased dramatically.
15 or 30 pound roofing felt is the most basic of underlayments and should only be used if there is no budget to pay for a better underlayment or if you just don’t care. It tears easily, wrinkles if it becomes wet and does not last the life of the roof covering. Wrinkles from wet felt can also transmit through asphalt shingles giving your roof a wrinkled appearance.
This is one of your biggest expenses as a homeowner and one of the most important. Without a roof, you have no protection for your family or belongings from the elements. Buy and install the best roof covering that you can and use a high quality, synthetic roofing underlayment, like Grace Tri-Flex. You roof will last longer and look better.