Glossary of Roofing Terms

A | B | C | D | E | F | G | H | I | J | L | M | N | O | P | R | S | T | W

A

Alligatoring

Cracking of the surfacing bitumen on a roof, producing a pattern similar to an alligator’s skin.

Asphalt

A dark material by product of processing crude oil or petroleum that can be further refined for roofing applications

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B

Backnailing

Blind nailing of roofing felts to a substrate along with hot-mopping to avoid slippage.

Ballast

A material, which uses impermeable layers of felt or membrane to prevent wind uplift of a loose-laid roof system.

Base sheet

A saturated felt placed as the first ply in a multi-ply bituminous roofing membrane.

Batten

Raised rib, in a metal roof, or a separate part of a metal roofing panel.

Bitumen

Refers to any substance composed principally of bitumen. Two basic types in roofing are asphalt and coal-tar pitch.

Blanket Insulation

Fiberglass insulation that comes in rolls form. Generally installed between metal roof panels and the supporting purlins.

Blister

An enclosed pocket of air-water vapor, caught between membrane plies.

Bridging

When membrane or base flashing is unsupported at a juncture.

Buckle

An upward displacement of a roof membrane that often occurs over or deck joints or insulation.

Building Code

The minimum construction requirements established by roofing experts and adopted by local authorities.

Built-up Roofing (BUR)

A semi flexible membrane made of plies of coated felts, saturated felts, mats or fabrics assembled in place with alternate layers of bitumen.

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C

Capsheet

Top ply of a built-up roofing membrane.

Caulk

A composition used for filling and sealing joints.

Coating

A layer of liquid material applied to a surface for appearance or protection.

Cold Process Roofing

A continuous, semi-flexible roof membrane, consisting of plies of felts, mats, or fabrics that are laminated on a roof with alternate layers of cold-applied roof cement and surfaced with a cold-applied coating.

Condensation

The conversion of water vapor to liquid.

Coping

A wall covering sloped to carry off water.

Cornice

A decorative horizontal molding.

Counter Flashing

Formed metal or elastomeric sheeting secured on or into a wall, curb, pipe, or rooftop unit, to protect the upper edge of a base flashing.

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D

Damp Proofing

Treatment of a surface to prevent the passage of water.

Degradation

A change in the physical properties and appearance of a material from exposure the elements.

Delamination

Separation of the laminated layers of a component.

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E

Eave

The lower edge of a sloping roof which projects beyond the wall.

Elastomeric Coating

A coating that can stretch at least twice its original length and recovering to its original dimensions.

Embedment

The process of pressing a felt, aggregate, fabric, mat, or panel uniformly and completely into hot bitumen to ensure contact at all points.

Emulsion

A mixture of water and bitumen.

Envelope

A continuous felt fold formed by wrapping and securing a portion of a base felt back up and over the felt plies above it. 

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F

Flat Roof

A horizontal or nearly horizontal roof with a very slight inclination.

Flange

The projecting edge of a rigid component, such as a metal edge flashing flange.

Flashings

Components used to weatherproof system edges at where the roof covering is interrupted or terminated.

Framed Opening

Framework and flashing which surround an opening in the roof.

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G

Gable

The vertical triangular portion of the end of a building.

Galvanized Steel

Steel coated with zinc for corrosion resistance.

Glaze Coat

The top layer of asphalt in a smooth surfaced built-up roof assembly.

Gravel

Coarse granular aggregate resulting from the natural erosion of rock.

Green Building Technology

The use of technology to reduce the impact on the environment, which includes recyclability, sustainability and the reduction of carbon dioxide emissions.

Grout

Mixture of cement, sand, and water used to fill cracks and cavities.

Gutter

A channel installed along the down slope perimeter of a roof to convey runoff water from the roof to the drainage system.

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H

Hip Roof

A roof, which rises by inclined planes from all four sides on the building.

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I

Incline

The slope of a roof expressed as a percentage.

Insulation

A material applied to reduce the transfer of heat.

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J

Joist

Small metal or wood beams that are parallel to each other to support the roof.

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L

Lap Seam

Occurs where overlapping materials are seamed, sealed or bonded.

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M

Membrane

A flexible or semi-flexible roof covering designed to exclude water from the roof.

Modified Bitumen

A bitumen modified by including one or more polymers.

Mop-and-Flop

A procedure where roof components are initially installed upside down next to their final locations and are coated with adhesive before being turned over and adhered to the substrate.

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N

Neoprene

A synthetic rubber used in liquid and sheet-applied elastomeric roof membranes.

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O

Overhang
A roof extension beyond the exterior wall of a building.

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P

Pallets

A wooden platform used for shipping materials.

Parapet

The part of a perimeter wall that extends above the roof.

Pig spout

A sheet metal flashing that directs the water out through the face of the gutter.

Pond

A roof area that retains water.

Primer

A thin, liquid-applied solvent-based bitumen used to improve the adhesion of additional applications of bitumen.

Protected Membrane Roof

Sometimes known as upside-down roof assembly it is the process of roof assembly with insulation on top of membrane instead of the other way around.
 
PVC Roofing

Highly-engineered, flexible, thermoplastic membrane roofing materials manufactured using an ultraviolet-resistant polyvinyl chloride and known for excellent weathering characteristics, strength and long-term flexibility.

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R

Rafter

Sloped structure that extend from the ridge or hip to the down slope perimeter or eave, designed to support the roof deck.

Reflective Roofing

Generally white in color, reflective roofing is designed to reflect more of the sun's rays and decrease the amount of heat transferred into a building.
Reinforced Membrane
A roofing membrane reinforced with felts, mats, fabrics, or chopped fibers.

Re-roofing

The removal of an existing roof followed by the installation of a completely new roofing system.

Retrofit

The modification of an existing roof to include new systems or components.

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S

Sealant

A material that has the adhesive and cohesive properties to form a seal used to fill and close joints.
    
Shingle

A small unit of prepared roofing designed for installation in overlapping rows.

Single Ply

A type of commercial roofing membranes that consist of flexible sheets of compounded synthetic materials.

Slope

The angle of incline, usually expressed as an angle.

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T

Tar

A dark semi-solid bituminous material.

Thermoplastic Roofing

Roofing membranes, which can be repeatedly softened by heating or hardened when, cooled. Thermoplastic membranes typically are seamed by heat welding with hot air or solvent welding.

Trim

The light gauge metal used in the finish of a building.
 
TPO membrane Roofing

Single-ply roof membranes constructed from ethylene propylene rubber that combine the durability of rubber with the performance of hot-air weldable seams.

Vent

An opening designed to release air, heat and water vapor from a building to the outside

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W

Waterproofing

Treatment of a roof surface to prevent the passage of water.

Wicking

The process of moisture movement by capillary action.

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