Roofing Terminology 101



Alligatoring occurs when seams open up or the tar and gravel cracks on your rooftop. This commonly happens to tar and gravel roofs at or near the end of their lifespan, which is typically 10-12 years. In most cases, the roof should be replaced as soon as possible when and if this happens.


Aluminum Gutters


Aluminum is a rust-resistant material popular with newer installations. You can purchase it unpainted or painted, and it can be installed relatively easily and quickly. Aside from it denting easily, aluminum gutters tend to see leak issues later in their lifespan after the metal expands and contracts due to the elements. 




A roof deck consists of sheathing and underlayment known as roofing felt. The material used to finish the roof determines deck types. Most roofs require solid plywood or oriented strand board sheathing, while wood shingle and tile roofs need spaced board sheathing.




Dormers create additional openings in your roof, which will affect your roof installation. One notable area is at the joints, which will need to be sealed with metal flashing to avoid water intrusion during rainfall. The style of dormer can also affect your roofing material. A shed dormer will decrease the slope of your roof over the opening. A gabled dormer often has higher pitches which will shed water more easily. Be sure to consult your roofing company before making any big decisions. 


Fascia Board


Fascia board is the exposed end of your roof. The gutter is normally attached to this.




Flashing is the metal or vinyl edging that is placed along roof intersections, dormers, chimneys, vent pipes and edges of the roof. It helps guide water away from roof joints and toward gutters. Most flashing is made of galvanized steel or aluminum. 




Gutters are the metal channels that are attached to the roof edges and used to draw water down and away from the house and its foundation. Most gutters consist of gutter sections, drop outlets and downspouts. Gutters can be constructed of aluminum, galvanized steel, vinyl, wood or copper.


Ice Dams


Ice dams are formed when heat from the attic melts snow at the ridge or peak of the roof causing an “avalanche” of snow and ice to overflow the gutters. The melted water can then back up under the shingles and work its way into the house.


Ridge Vent


A ridge vent is a special vent that sits along the top ridge of your roof. Like other vents, it allows your attic to breathe, but it sits underneath the roofing material, making it less visible than standard vents. Ridge vents help to prevent ice dams and improper snow melt off.


Roofing Felt


Roofing felt is the protective layer that sits between the roof sheathing and the shingles.


Roof Pitch and Slope


Roof pitch and roof slope are two terms that are often used interchangeably, but they actually mean different things. Slope is described in inches of vertical rise per foot of horizontal run. For example, a gently sloped roof that rises 4 inches for every 12 inches of house covering is said to have a 4-in-12 slope. Roof pitch is expressed as a fraction, the ration of rise to the total span of the entire roof. The same gentle 4-in-12 slope translates into a 1:6 pitch.


Roof Surface


A roof’s surface is the area on which all the roofing material sits. Roofing surfaces can be made of a variety of materials. The most common material in the U.S. is plywood with a covering of sheathing, felt and roofing shingles.




About 80% of homes in the U.S. have asphalt shingle roofs. These are constructed of 12 x 36 inch sections that look like individual shingles when installed.




Soffits are vents under the roof overhang that allow your attic to breathe.