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Common Roofing Materials

Frequently Asked Questions

Getting Up on Roofs: Tips From the Experts

Glossary of Common Roofing Terms

A - C

D - L

M - R

S - Z

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Glossary of Common
Roofing Terms

A - C

D - L

M - R

S - Z



Mansard: (1) A steep-sloped roof located at the perimeter of a building and usually used for decorative purposes; (2) The upper story formed by the lower slope of a mansard roof.

Mansard Roof: A steeper roof that terminates into a lower sloped roof at its high point.

Mastic: A thick adhesive material used as a cementing agent for holding a roofing or waterproofing membrane in place.

Material Safety Data Sheet (MSDS): Information provided by a manufacturer that describes the characteristics of chemicals in a given product, as well as other information such as emergency procedures and safe handling.

Mechanical Damage: Damage to a roof by means of items puncturing or otherwise unnecessarily penetrating the roof system or any of its components.

Mechanical Fasteners: Devices such as screws, plates, battens, nails, or other materials that are used to secure roofing materials to the deck.

Membrane: The portion of the roofing system that serves as the waterproofing material. A membrane can be composed of one material or several materials laminated together.
Metal Flashing: Roof components made from sheet metal that are used to terminate the roofing membrane or material along roof edges. Metal flashings are also used in the field of the roof around penetrations.

Mineral Fiber: Inorganic fibers of glass or rock.

Mineral Granules: See Granules.

Mineral-Surfaced Roofing: Roofing materials with a top surface consisting of mineral granules.

Modified Bitumen: A bitumen modified by the addition of one or more polymers, such as Atactic Polypropylene (APP) or Styrene Butadiene Styrene (SBS), to enhance its natural properties, especially elasticity.

Mopping: To apply hot asphalt or coat tar using a hand mop or mechanical applicator


Nailer: A piece of lumber that is secured to the deck, walls, or curbs to receive fasteners for roof membranes.

Nailing Pattern: The specific method or pattern at which nails are to be applied.

Nesting: To overlay existing shingles with new shingles and butt the top edge of the new shingle up against the bottom edge of the existing shingles.

Nosing: Metal flashing bent at a 90º angle and installed around roof perimeters, curbs, platforms, etc. in order to protect the edge of the roofing system. Nosing should not be used in place of drip edge.

NRCA: National Roofing Contractors Association.


Open Valley: A valley where both sides of the roofing material are trimmed back from the centerline to expose the valley flashing material beneath.

Organic Felt: An asphalt roofing base material manufactured from cellulose fibers.

Organic Shingle: An asphalt shingle reinforced with organic material manufactured from cellulose fibers.

OSB: Oriented Strand Board, which is often used as roof sheathing in place of plywood.

Overlay: See Re-Cover.

Overspray: The loss of spray particles (from coatings, SPF, etc.) in the air.


Pan Flashing: A sheet metal flashing that covers an equipment platform and is designed to counterflash the base flashings surrounding the platform.

Parapet Wall: That part of a perimeter wall that extends above the surface of the roof.

Penetration: Any object that pierces the surface of the roof.

Perlite: A natural volcanic glass that is used in lightweight insulating concrete and fire-resistant rigid insulation board.

Pipe Boot: A prefabricated flashing piece that is used to flash around circular pipe penetrations. Also known as a Roof Jack.

Pitch: A term used to describe Roof Slope. Also shorthand for Coal Tar Pitch.

Pitch Pocket (a.k.a. Pitch Pan): A flanged piece of flashing material placed around irregularly shaped roof penetrations and filled with grout and a pourable sealer to seal around the penetration to prevent moisture entry.

Ply: A layer of felt or other reinforcement material in a roof system.

Polymer Modified Bitumen: See Modified Bitumen.

Ponding: The accumulation of water at low-lying areas on a roof.

Positive Drainage: The drainage condition of a roof where all water is gone from the roof surface within forty-eight hours of precipitation under normal drying conditions.

Press Brake: A mechanical device used to form sheet metal into desired shapes and profiles.

Primer: A material that is applied to a surface in order to increase that surface’s ability to adhere to or work in conjunction with a subsequently applied material.

Protected Membrane Roof Assembly (PMRA): A roof assembly in which the insulation and ballast are placed on top of the membrane. Also known as an Inverted Roof Membrane Assembly (IRMA).

Purlin: A horizontal secondary structural member used to transfer loads from the primary structural members.


No definitions found.


R-Value: The measure of a material’s resistance to heat flow. The higher a material’s R-value, the more it insulates.

Rake: The sloped perimeter edge of a roof that runs from the eaves to the ridge. The rake is usually perpendicular to the eaves and ridge.

Re-Cover (Overlay): The installation of a new roof system directly over an existing roof system.

Reglet: A receiver, usually made of sheet metal, to which counterflashings are attached. Reglets can be surface-mounted or part of the wall assembly.

Re-roofing: The procedure of installing a new roof system on an existing building.

Ridge: The line where two planes of roof intersect, forming the highest point on the roof that runs the entire length of the roof.

Ridge Cap: Material applied over the ridge or hip of a roof.

Ridge Vent: An exhaust venting device located at the ridge of a roof.

Roll Goods: The term used for all roofing materials that come in rolls.

Roof Assembly: A term used to describe all of the components of a roof system, including the structural roof deck.

Roof Curb: A frame or platform on which rooftop equipment such as HVAC units, exhaust fans, skylight, etc. is mounted.

Roof Jack: (1) A steel bracket fastened to the roof that is used to support toe boards; (2) A term used to describe a Pipe Boot.

Roof Slope: The angle made by the roof surface plane with the horizontal plane and expressed as the amount of vertical rise for every twelve inch (12") horizontal run. For instance, a roof that rises four inches (4") for every twelve inch (12") horizontal run, is expressed as having a "four in twelve" slope; often written as "4:12." Expressed as a percentage, the slope would be 33%, which is equal to 4 divided by 12. Also known as the Pitch of a roof.

Roof System: Multiple roof components assembled to provide waterproofing (and sometimes insulating) capabilities for a structure. 

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