The manufacture of asphalt roofing materials has been undergone from the 1890s. Today asphalt shingles cover 70 to 80 percent of the roofs in united states. It has now spread to different part of the world.
The asphalt roof shingles are very attractive, versatile and provide high fire and wind resistance. The shingles cost is economical which make it relatively inexpensive in terms of aesthetics and the durability it provides to the building.
The asphalt shingles can be very easily installed and requires little maintenance. The normal life expectancy of the asphalt roof shingles is in the range of 15 to 20 years. The fiberglass shingles provides a life expectancy of 20 to 30 years.
Fig.1. Asphalt Roof Shingles
Types of Shingles for Roof
The organic based asphalt shingles consist of a base mat composed of cellulose fibers made from recycled paper or the wood chips and cotton or the wool rags. But presently it is made of asphalt -saturated roofing felt. It is coated with asphalt on the both sides as shown in the figure below.
Fig.2: Components of Asphalt Shingles
The strength for the shingles is provided by the base mat. The base material is in a saturated state. It is covered with a flexible asphalt that has a high melting point which is called as the saturant.
Ground limestone, slate, trap rock or other inert materials are used to reinforce the saturant which is mineral stabilizers. The coarse mineral granules are pressed on the exposed phase of the asphalt coating which provides color for the asphalt. This exposed phase helps the shingle to resist the weather and the fire.
The materials that used as coarse mineral surfacing are natural colored slate or ceramic coated rock granules. Each shingle’s back side is covered with a talc, mica or sand. This will prevent the shingle to prevent sticking to each other.
The first entry of fiberglass was in the late 1950s. By 70s they have grown up as traditional asphalt shingles.
The fiberglass asphalt shingle has a base mat that is saturated and covered by means of flexible asphalt. It is also surfaced with mineral granules.
When compared with cellulose fiber mat, the fiberglass shingles have a very less weight and thickness. Compared with organic asphalt shingles, the fiberglass shingles consist of more asphalt.
The organic shingles have chances to soak the water up from the underneath. This result in the curling up of the bottom. This made the demand of organic-based shingles to decrease.
Deck Requirements for Asphalt Shingles
The asphalt shingles are installed over a solid roof deck. In general, the slope necessary to install asphalt shingles is in the range from 4 in 12 through 21 in 12 by employing standard installation method.
The asphalt shingles can also be used in slopes in the range of 2 in 12 which are flat and 21 in 12 that are steeper in nature. But special application procedures apply.
Types of Asphalt Shingles
Two types of asphalt shingles are mainly used in roof construction. One is three-tab shingles. This has two slots, that divide the exposed part of the shingle into thirds. The second one is the laminated shingles or architectural and dimensional shingles.
These are presently used in a wide range. The laminated shingles consist of two layers that make it more thicker and wind resistant.
Repair of Asphalt Shingles
Shingles are available from the market in the form of strips. They are laid over the concrete decks or boards laid over the roof area and pressed by means of nails.
Proper alignment of the strips helps in filling up the roof by shingles in a systematic manner, leaving no gaps and spaces.
Fig.3. Properly aligning the shingle strip over the end of the roof and pressing by nails to the boards
Fig.4. Each Strip is properly aligned and pressed to avoid gaps
Sometimes the reason of missing shingle may result in leaks or worn outs. Or there are situations where we have to disturb the shingles to install a roof vent or plumbing vent.
Such removal is advised to be done when the shingles are in a cooled state. This will make the adhesive beneath the layer to be brittle and easier for removal. Removal under hot conditions will tear the roof shingle.