Madison Roofing: Article About Types Of Roof Underlayment Materials
Roof underlayment materials provide added protection for the roof from moisture and, thus, increase the lifespan of the home's roofing system. Underlayment is a water resistant, breathable material that is laid between the roof deck and the shingles. There are three basic types of underlayment commonly used, which include asphalt felt, rubberized felt and synthetic materials. Consulting a Madison roofing professional will ensure the proper underlayment is installed on the home's roof.
For many years, the most common type of underlayment was asphalt saturated felt. This type of underlayment is relatively inexpensive and is easy to install over wood decking. The sheets of underlayment are overlapped and installed with staples or plastic cap roofing nails. In ideal conditions, the asphalt saturated felt should provide an adequate and breathable moisture barrier. There are some problems associated with his type of underlayment, however. Over time, the materials in the asphalt will start to break down when exposed to heat, either from the sun or from inadequate attic ventilation. This can cause the material to become more fragile and can increase moisture absorption as a result. If shingles break or blow off in high winds, the asphalt felt material will deteriorate quickly, allowing moisture to penetrate the roof decking and compromise the roof system.
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Asphalt felt can also become damaged during installation from excessive foot traffic or exposure to the elements.
Rubberized felt can also be used as a roof underlayment. This rubberized material is much more moisture resistant than the asphalt felt and is self-healing around nail holes and staples. Some rubberized felt underlayments have a polymer coating added that functions to greatly decrease the chance of moisture wicking into the material. An adhesive is sometimes added to the back of the material. The rubberized felt material is thus less prone to wrinkling and is slip resistant, which contributes to a safer installation.
Synthetic underlayments are an improvement on both types of felt underlayments. These come in a variety of materials and are sometimes targeted for special installations. Some waterproof underlayments are designed for installation on the lower portion of sloped roofs, which prevents wind-blown rain and snow from seeping in. Other synthetic materials are specifically designed for use under metal or tile roofs. Synthetic underlayments are lighter weight and stronger than their felt counterparts. They are slip resistant, self-adhesive and do not absorb moisture. They are resistant to UV degradation and can be exposed to the elements for an extended period of time before damage occurs. The disadvantage of these materials is that they are more expensive. A roofing contractor can decide which type of underlayment works best for each specific installation.