Alamo Heights Roofing: Article About Roof Underlayment
Roofs have a multitude of enemies. One of the worst is water, but wind, sunshine, insects and pests take a toll. Besides the elements, workers repairing one part can accidently damage another area. Any kind of tear or break in the roofing materials will allow an unwanted intrusion into the building's interior. Alamo Heights Roofing understands how to use underlayment to add an extra barrier between a structure and the elements.
Roofing material isn't usually fastened directly to the rafters. Instead, a roof deck is built over the rafters to help support and secure the rest of the roof. Roof decks may be constructed of wood, particularly plywood or OSB, metal, gypsum or even concrete. Underlayment is then attached to the roof deck and roofing material installed over the underlayment. The result is three layers of protection.
Traditional underlayment is made of felt paper saturated with asphalt. The type of asphalt used is a byproduct of refining crude oil. The term organic doesn't mean the felt is a "green" product. It means the felt is made from cellulose, a plant product, rather than fiberglass. The underlayment is not waterproof, but it allows the roof to "breathe." Felt has fallen out of favor partially because of its weight and partially because of the cost of asphalt. It also tears easily and any holes made by the fasteners attaching it to the deck require additional sealing.
Have a question regarding commercial roofing or insulation? Please ask a roofing expert from Tony's roofing of Alamo Heights TX.
Rubberized asphalt refers to underlayment in which the materials have been modified, usually with polymers. Another name for it is modified bitumen or "mod-bit." Bitumen refers to the fact that asphalt is a hydrocarbon. Depending on the polymers and the process used, the resulting material will feel like rubber or plastic. It usually has an adhesive on one side to make the final product easier to install. Rubberized asphalt underlayment also self-seals around the nails or fasteners used to attach it to the roof deck.
Synthetic underlayment is frequently used in contemporary homes. It's made from polypropylene or polyethylene, which are the same materials used in making a multitude of plastic and fabric products. Synthetic underlayment is lighter and stronger than the asphalt types. It's also more resistant to the elements.
In extreme climates an additional layer of protection is used to prevent damage from snow and ice buildup. It's an adhesive membrane commonly known as ice and water shield. It isn't used to cover the whole roof. Instead, it is installed along the first three feet or so of the roof where wind could blow moisture under the roofing material. It may also be placed around chimneys and vents. Once placed, the membrane can't be moved.