Roof Replacement Terms and Definitions

Unfortunately, at this point in the history of building construction, we have yet to develop a roofing system that will last forever. Therefore, it is very likely that each of us will have to deal with a roof replacement.

After all, the roof is the most important structural component of any building. Without a quality, weather-resistant roof, every other component in a building will be destroyed in no time. Paint materials, drywall, frames, and flooring just aren’t designed to withstand Mother Nature. Indoor spaces and people need protection from the elements.

Here are some roofing terms that can 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 is sold by the square, and roofers generally calculate costs and price based on the total number of squares.

Decking or Sheeting: the flat layer of material adhered to the ceiling joists. Many old houses and buildings have wooden plank decks. Most modern residential buildings have plywood or oriented strand board (OSB) decking that is manufactured in 4 x 8 foot sheets (sometimes called sheets). The most common thickness of roof deck in use today is 7/16 “. The base and shingles are attached to the roof deck.

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. Post-2006 shingles are referred to by many roofers as asphalt shingles, where the correct technical term is actually composition shingles.

Composition Shingles – Modern shingles made from a mix of asphalt and fiberglass. The asphalt / fiberglass body of the shingle is covered with a protective granular wear layer.

Granular Wear Layer – The ceramic top layer of a composition tile provides stiffness (protection against hail, debris, and puncture), UV protection, and also provides color.

Architectural / Laminate / Dimensional Shingles – All terms refer to popular modern shingles made from multiple layers of asphalt / fiberglass (laminate) material providing increased strength, longevity, and a jolt-like appearance.

Underlayment – The layer of material that is applied to the roof deck before shingles are installed. The most common underlayment is felt paper (tar) 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 proven to have longevity and performance advantages over traditional roofing felt.

Ice and Water Barrier or Weather Barrier – Underlayment manufactured with adhesive on one side and used to protect roof overhangs and valleys from ice dams and pools of water. Installing an ice and water barrier is a critical step to prevent damage to the roof deck from water and / or ice that collects from gutters and passes under shingles. Most municipal building codes require that a minimum of the first three feet of the roof eaves be covered by an ice and water barrier.

Roof Exhaust Vent – The exit space that is left open at the highest part of the roof to provide adequate ventilation and the release of hot air. Roof vents can be either the old-style box type, vents, or a modern ridge vent system. The structure and style of your roof will determine which style of ventilation will work best.

Roof Inlet Vent – The intake space that is left open at the lowest part of the roof to provide adequate ventilation and infusion of cool outside air. The intake vents can be gable vents or ceiling vents. The structure and style of your roof will determine which style of ventilation will work best.

It is important to do your homework before discussing your project with a roofer or roofing company. There are a myriad of options for shingles, subfloors, vents, and decking, and great variation in the cost of each type of material. Each component of a roof is critical, as each piece must work together as a system once properly installed. A failure of one component could result in a failure of the entire system.