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Our Glossary of Roofing Terms

We know that it is sometimes difficult to understand all the terms related to our services. At Century Roofing Limited, we hope to educate our clients on any terms undefined. Hence, we have compiled a handy list of some of the most common roofing terms to help you understand every step of your roofing process.


The process by which one material is permeated by another material like liquid, gas or moisture.

Aggregate is usually made up of rock, stones, crushed stones, gravel or marble chips and is used for roof surfacing.

Cracking occurring on surface bitumen that closely resembles alligator skin.

Apron flashing
The flashing that covers the juncture of the top of a sloped roof and a vertical wall or adjoining roof.

A mix of sand or gravel and bitumen that is used for surfacing roads and roofs.

Asphalt felt
Asphalt-soaked felt used as underlay beneath other roofing materials. Asphalt felt provides an added layer of protection against water and moisture damage.


Back surfacing
Fine, granular material added to the backs of shingles to keep them from sticking together.

A heavy material that is used as an anchor to hold roof membranes in place.

Base flashing

Roof membrane material that protects the joints between the roof and adjoining walls, or other vertical surfaces, from exposure to water and weather.

Base ply

The lowest ply of roofing material in the roofing system.

Base sheet
Asphalt-coated felt that is used as the first ply in certain roof systems.

Thin strips of wood used to provide a fixed point to which other roofing materials, like shingles or tiles, can be attached.

A naturally occurring black viscous material made up of decomposed organic materials and hydrocarbons that is used for roof surfacing.

Built-up roof membrane
A multi-layered roof membrane made up of alternating layers of felts, fabrics or mats and bitumen.

Butt flashing
The butt flashing is a metal strip used to keep water from seeping into the upper edges of the membrane base flashing, wall flashing or primary flashing.

A rubber-like material that is used as a sealant or adhesive.

Butyl tape
A preformed sealant tape that is used to close joints and seams.


A part of the roof structure that overhangs an entrance or a door.

Cant Strip
A three-sided strip of wood cut on an angle to provide a sloped transition between the roof deck and an adjacent wall. Cant strips help with waterproofing by closing the gap between the roof deck and any walls.

Cap Flashing
Cap flashing is a form of flashing that keeps water from getting into the upper edges of the membrane base or other types of flashing.

Cap Sheet
Used in built-up roofing, a cap sheet is the topmost roofing sheet that serves to protect the lower layers of a roof membrane. It’s usually coated with a granular substance and can help to extend the life of the roof.

Closed Valley
A valley is the line where two separate sections of the roof meet and drain water off the roof. A closed valley is when the shingles on one side completely cover the shingles on the other side.

Closure Strip
A strip of metal or other material that is used to close gaps in between membranes or other joints.

A piece of metal, masonry or stone that is used to protect the top of part of a wall from weather and water.

Counter flashing
A shaped piece of metal sheeting that is used to cover and weatherproof the upper edge of the base flashing.

A small roofed structure that sits on top, usually in the center, of a larger roofed structure.

When shingles start to warp at the edges, forming a cup shape. Cupping is usually a sign that shingles contain a manufacturer’s defect or were installed incorrectly.


An important structural component of the roof. The deck supports the weight of the rest of the roofing system.

Double gravelling
The process of applying two layers of bitumen and aggregate to a built-up roof.

A pipe that is used to divert runoff water towards the ground or the storm drain.

Drip edge
A custom sheet of metal designed to extend shingles beyond eaves and gutters so that water can’t get behind the fascia board.


The part of the roof that extends beyond the exterior walls of the house.

Expansion joint
An assembly between two building elements that is designed to allow free movement between the elements without damage to the roofing or waterproofing system.

A manufacturing process used to make some types of single-ply roofing membranes.

Either a small dormer with an arched roof line or a small shed roof projecting from the main roof.


The vertical band is either wood or aluminum and covers the ends of the rafters or trusses, it goes behind the eavestrough and up the gable ends to provide waterproofing protection for the building’s interior.

A metal sleeve that is placed inside a gutter at the top that protects and preserves the gutter’s original shape.

A rim or collar that is used to both strengthen and attach a rigid component to the roofing structure.

As part of a weather-barrier system, flashing refers to the components used to seal the roof system at its edges to prevent water from soaking through the roof and causing damage.


The triangular part of an exterior wall of a building that sits under the sloping roof but above the eaves and that encloses the end of a pitched roof.

A two-sided roof with two pitches on each side with a shallow slope above a steeper one.

Gravel stop
A gravel stop is a type of metal edge flashing that is installed around the perimeter of the roof to provide an edge for the roofing material.


Hex shingles
Hex shingles have a hexagonal shape after installation is complete.

The edge created by the intersection of two sloping roof planes.

Hip Roof
A roof with no gables or vertical slides; all of the sides on a hip roof gently slope towards the walls.

A mechanical device used for lifting or lowering a heavy load.

HVAC stands for Heating, Ventilating, and Air Conditioning units or equipment.


Ice dam
A block of ice formed by refreezing meltwater at the overhang of a steep roof. When ice blocks the gutters, it is impossible for meltwater to escape, which then results in excess water leaking underneath roofing materials and into the building.

Impact resistance
The ability of the roofing assembly to resist external damage.

Infrared thermography
Also called thermal imaging, infrared thermography is a part of a roof system analysis used to locate the presence of moisture and leaks.

Intake ventilation
The intake vent is the part that draws fresh air into the roof’s ventilation system.

Interlocking shingles
A method of interlocking individual shingles to increase the wind resistance of the roof system.


The metal or wood beams that are arranged parallel from wall to wall and are used to support a floor, ceiling, or roof of a building.


Laminated shingles
Stronger and more decorative than other shingles, laminate shingles are made up of two pieces of shingle that are laminated together to create strength and durability.

Lap cement
An asphalt-based cement that is used to adhere roll-roofing materials together.

Loose-laid membranes

Held in place with a ballast, loose-laid membranes are only attached to the substrate at the perimeter of the roof.


Mansard roof
Also called a French roof, a mansard roof is a steep, four-sided gambrel-style hip roof that terminates into a flat roof at its high point.

A pliable sheet that serves as the waterproofing component in a roofing or waterproofing assembly, and whose primary function is to keep water from penetrating the roof.


A synthetic, rubber-like material that is used in roof membranes or flashings as a weatherproofing agent.

A re-roofing method where new shingles are laid over the top of old shingles with the edge of the new shingle being butted against the bottom edge of the old shingle tab.


Open valley
A roofing method that leaves the valley flashing exposed and free of shingles to allow water to run off down the opened valley.


Parapet Wall
The part of a perimeter wall that runs along the edge of the roof.

An aggregate that is used in lightweight, insulating concrete and preformed insulation boards.

Pitch-pocket (Pitch-pan)
An enclosure fashioned out of sheet metal and sealed with grout and bitumen that is used to patch a roof penetration.

Puncture resistance
The extent to which a material can resist puncture or perforation.

The horizontal secondary structural member in a roof frame that supports loads from the primary structural framing.


Reinforced membrane
Roofing membrane that has been strengthened with fibres, mats, sheeting or other reinforcement materials.

Release tape
A sheet of plastic applied to the back of self-sealing shingles to prevent them from sticking together.

Roofing tape
Asphalt-saturated tape that is used in conjunction with asphalt cements for flashing and repairing asphalt roofing.


Located between drains, or in a valley, a saddle is a slightly raised structure that is used to direct surface water off the roof.

Self-adhering membrane
Protected by release paper, a self-adhering membrane is coated with adhesive and can adhere to a substrate without the application or use of any additional adhesive.

The enclosed underside of any architectural structure such as a roof eave.

Soil stack
Part of the plumbing system, a soil stack is a sanitation pipe that penetrates the roof and is used to vent gases out of the building.

Step flashing
Individual pieces of flashing that are overlapped and “stepped” on a vertical surface. Used around chimneys and other projections on the roof.

Usually the roofing deck. The substrate is the underlying surface upon which the roofing membrane is applied.


Test cut
A sample cut out of the roof that is used to examine all of the components of the roofing membrane and determine if there are any issues with the membrane.

Thermal shock

The contraction of the membrane that can occur when it is exposed to rapid changes in temperature.


Underlayment is used to add a layer of weather and waterproofing to the roof deck. It is a synthetic felt in varying weights and surface finish, installed between the roof deck and the rest of the roof system.


The ‘V’ shaped depression that is formed by the intersection of two sloping sections of roof. The valley provides a channel for water to run off the roof.

Vapor retarder
Any material that is used to damp-proof, or restrict the passage of water vapor through a roof system.


Waterproof underlayment
Waterproof underlayment is designed to seal the roof deck and provide extra waterproofing for areas susceptible to leaks.

Wind uplift
Wind uplift is caused by the deflection of the wind at the roofs edges. During very strong winds, wind uplift can result in the membrane pulling away from the deck.

Woven valley
The valley flashing is not exposed in this method of valley construction, but rather, the shingles on both sides of the valley are woven together in an overlapping pattern.

For more information on our roofing services or to speak to one of our experts for your new project, contact Century Roofing Limited today! Our team will be happy to answer all your questions.

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