Two types of base materials are used to make asphalt shingles: A formerly-living organic base and fiberglass base. Both types are made in a similar manner with asphalt or modified-asphalt applied to one or both sides of the asphalt-saturated base, covered with slate, schist, quartz, vitrified brick, stone, or ceramic granules and the back side treated with sand, talc or mica to prevent the shingles from sticking to each other before use.
The top surface granules block ultra-violet light which causes the shingles to deteriorate, provides some physical protection of the asphalt and gives the shingles their color. Some shingles have copper or other materials added to the surface to help prevent algae growth. Self-sealing strips are standard on shingles to help prevent the shingles from being blown off by high winds. This material is typically limestone or fly-ash-modified resins, or polymer-modified bitumen. American Society of Civil Engineers ASTM D7158 is the standard most United States residential building codes use as their wind resistance standard for most discontinuous, steep-slope roof coverings (including asphalt shingles) with the following class ratings: Class D – Passed at basic wind speeds up to and including 90 mph; Class G – Passed at basic wind speeds up to and including 120 mph; and Class H – Passed at basic wind speeds up to and including 150 mph.
An additive known as styrene-butadiene-styrene (SBS), sometimes called modified or rubberized asphalt, is sometimes added to the asphalt mixture to make shingles more resistant to thermal cracking, as well as more resistant to damage from hail impacts. Some manufacturers use a fabric backing known as a “scrim” on the back side of shingles to make them more impact resistant. Most insurance companies offer discounts to homeowners for using Class 4 impact rated shingles.
Asphalt shingles have varying qualities which help them survive wind, hail, or fire damage and discoloration.
- The American Society of Testing Materials (ASTM) has developed specifications for roof shingles: ASTM D 225-86 (Asphalt Shingles (Organic Felt) Surfaced with Mineral Granules) and ASTM D3462-87 (Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules), ASTM D3161, Standard Test Method for Wind-Resistance of Asphalt Shingles (2005),
- Many shapes and textures of asphalt shingles are available: 3 tab, jet, “signature cut”, Art-Loc, t-lock, tie lock, etc. Architectural (laminated) shingles are a multi-layer, laminated shingle which gives more varied, contoured visual effect to a roof surface and add more resistance for water. These shingles are designed to avoid repetitive patterns in the shingle appearance. Special shingles are needed for the eaves starter course and ridge caps. Laminated shingles are heavier and more durable than traditional 3-tab shingle designs.
- Solar reflecting shingles help reduce air conditioning costs in hot climates by being a better reflective surface.
- Wind damage: Asphalt shingles come in varying resistance to wind damage. Shingles with the highest fastener pull through resistance, bond strength of the self seal adhesive, properly nailed will resist wind damage the best. Extra precautions can be taken in high wind areas to fasten a durable underlay and/or seal the plywood seams in the event the shingles are blown off. UL 997 Wind Resistance of Prepared Roof Covering Materials class 1 is best Wind Resistance roof standard and ASTM D 3161 class F is best for bond strength.
- Hail damage: Hail storms can damage asphalt shingles. For impact resistance UL 2218 Class 4 is best. This increases it surviving hail storms but the shingles become more susceptible to hail damage with age.
- Fire resistance: Forest fires and other exterior fires risk roofs catching on fire. Fiberglass shingles have a better, class A, flame spread rating based on UL 790, and ASTM E 108 testing. Organic shingles have a class C rating.
- Locking shingles: Special asphalt shingles are designed to lock together called tie lock or T lock.
- Durability Shingle durability is ranked by warranted life, ranging from 20 years to lifetime warranties are available. However a stated warranty is not a guarantee of durability. A shingle manufacturer’s warranty may pro-rate repair costs, cover materials only, have different warranty periods for different types of damage, and transfer to another owner.
Shingles tend to last longer where the weather stays consistent, either consistently warm, or consistently cool.