Unfortunately, at this point in the history of building construction we have yet to develop a roofing system that will last forever. Therefore, each of us will more than likely have to deal with a roof replacement.
The roof, after all, happens to be most important structural component of any building. Without a quality, weather-tight roof, all other components of a building will be destroyed in short order. Paint, drywall, framing, and flooring materials are just not engineered to withstand Mother Nature. Interior spaces, and people, need protection from he elements.
Below are some roofing terms that may be helpful during the decision making process:
Square – A unit of measure commonly used in roofing and siding that equals 10 feet by 10 feet or 100 square feet (1 square equals 100 square feet). Most roofing material is sold per square, and roofers generally calculate costs and price based on the total number of squares.
Decking or Sheeting – The flat layer of material attached to the roof joists. Many older homes and buildings have wood plank decking. Most modern residential buildings have plywood or orient strand board (OSB) decking that is manufactured in 4 foot x 8 foot sheets (sometimes called sheeting). The most common thickness of roof decking used today is 7/16″. Underlayment and shingles are attached to the roof decking.
Asphalt shingles – Organic based shingles that were discontinued in 2006 due to poor performance and many class-action lawsuits. The term asphalt shingle is often still used today as a misstatement. Many roofers refer to post 2006 shingles as asphalt shingles where the correct technical term is actually composition shingle.
Composition Shingle – Modern shingles manufactured with an asphalt/fiberglass mixture. The asphalt/fiberglass body of the shingle is covered with a protective granular wear-layer.
Granular Wear-Layer – The ceramic top coating of a composition shingle provides rigidity (protection from hail, debris, and punctures), UV protection, and also provides the color.
Architectural / Laminated / Dimensional Shingle – All terms refer to the modern popular shingle manufactured with several layers of asphalt/fiberglass material (laminated) that provide added strength, longevity, and a shake-like appearance.
Underlayment – The layer of material applied to the roof decking prior to installing shingles. The most common underlayment is felt (tar) paper in 15 or 30 pound options. There are many new synthetic products available that are made with waterproof/breathable material (similar to house wrap). Synthetic underlayment has been tested to have advantages in longevity and performance versus traditional roofing felt.
Ice and Water or Weather Barrier – Underlayment manufactured with adhesive on one side and is used to protect roof eaves and valleys from ice dams and water back-ups. Installing ice and water barrier is a critical step in preventing damage to roof decking by water and/or ice backing up from the gutters and going underneath the shingles. Most municipal building code requires a minimum of the first three feet of roof eaves to be covered by ice and water barrier.
Roof Exhaust Vent – The outflow space left open on the highest portion of roof to provide for proper ventilation and release of hot air. Roof vents can be the older style box type, power vents, or a modern ridge vent system. The structure and style of your roof will determine which style of vent will work best.
Roof Intake Vent – The inflow space left open on the lowest portion of roof to provide for proper ventilation and infusion of cool, exterior air. Intake vents can be gable vents or soffit vents. The structure and style of your roof will determine which style of vent will work best.
It is important do your homework prior to discussing your project with a roofer or roofing company. There are vast amounts of choices for shingles, underlayment, vents, and decking, and a huge variation in cost for each type of material. Each component of a roof is critical, as each piece should work together as a system once installed properly. A failure of one component could result in a failure of the whole system.