Dictionary of Roofing Terms

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Absorption: The act or process of retaining foreign particles such as gas or liquid without transmission of these particles.

Acid Etch: (1) The use of a strong acid to remove the surface of concrete thereby exposing the aggregate. (2) The use of a strong acid to etch the surface of material such as metal in order for that material to accept a primer or Spray Polyurethane Foam.

Acrylic Coating: A coating system with an acrylic resin base. Most Acrylic resins now contain strands to give a much greater overall strength and to help with the bridging of gaps

Acrylic Resin: A synthetic resin of the thermoplastic type made by the polymerisation of an acrylic compound, e.g. methyl acrylate, methyl methacrylate. 

Adhere: The clinging of one surface to another; either molecularly or otherwise.

Adhesion: The state of adhering

Aggregate: A surfacing or ballast for a roof system. Aggregate can be rock, stone, crushed stone or slag, water-worn gravel, crushed lava rock or marble chips.

Aluminium: A non-rusting metal used in roofing for metal roofing and the fabrication of gutter and flashings.

Alvadac: Trade name for a range of EPDM products

Ambient Temperature: The temperature of the air.

Anchor Bolts:  Bolts which fasten columns, girders or other members to concrete or masonry.

Angle Iron: A piece of iron that forms a right angle.

Anodizing (Aluminium Anodic Oxide Coating) - A process of coating aluminium by electrolytic
oxidation resulting in a thin film of aluminium oxide of extreme hardness. Dye-colouring is possible
by impregnation during the process.

Application Rate: The rate at which a material is applied per unit area.

Apron Flashing: A flashing located at the low end of a curb or penetration.

Architect: A tradesman who designs and produces plans for buildings, often overseeing the building process.

Architectural Panel: A metal roof panel that usually requires solid decking underneath.

Area Divider: A flashed assembly usually extending above the surface of the roof that is anchored to the roof deck. It is used to relieve thermal stresses in a roof system where an expansion joint is not required, or to separate large roof areas.

Asbestos: An incombustible fibrous mineral form of magnesium silicate formerly used for fireproofing and sometimes used for the reinforcement of roofing materials.

Atactic Polypropylene: A group of high molecular weight polymers formed by the polymerization of propylene.

Attic: The open area above the ceiling and under the roof deck of a steep-sloped roof.

Auger: Mainly used in carpentry, a wood-boring tool used to bore holes.

Back coat - (Metal sheeting) A coating applied to the back or unexposed side. Its purpose is to prevent corrosion of
the reverse side. It is closely controlled for colour, gloss and applied dry film thickness. Not to be
confused with a wash coat.

Back-Nailing: The method of fastening the back or upper side of a ply of roofing felt or other component in a roof system so that the fasteners are covered by the following ply.

Back-Surfacing: A fine mineral material on the back side of roofing materials such as roll roofing to keep them from sticking together while packaged.

Ballast: A material installed over the top of a roof membrane to help hold it in place. Ballasts are loose laid and can consist of aggregate, or concrete pavers. The ballast used for EPDM is generally above 10mm diameter and is smooth (No Quarry Gravel) river gravel is usually the best.

Bar Joist: See Steel Joist.

Barometer: Instrument for measuring atmospheric pressure.

Barrel Roof: A roof configuration with a partial cylindrical shape to it.

Base Flashing (membrane base flashing): Plies of roof membrane material used to seal a roof at the vertical plane intersections, such as at a roof-wall and roof-curb junctures. (See also Flashing.)

Base Ply: The primary ply of roofing material in a roof system.

Base Sheet: An asphalt-impregnated, or coated felt used as the first ply in some built-up and modified bitumen roof systems.

Batten: (1) A strip of wood usually fastened to the structural deck for use in attaching a primary roof system such as tile; (2) A plastic strip, wood strip, or metal bar which is used to fasten or hold the roof and/or base flashing in place, A.K.A. Termination Bar, also used for fixing trims to the perimeter of low pitch roofs.

Batten - (Metal sheeting) A broad, formed strip of metal put over a roof seam for decorative purposes and to conceal
fasteners.

Beam: Structural support member (wood, steel, concrete) that transfers weight from one location to another.

Bermuda Seam: A metal roof that has a step profile.

Bird Bath: Small, inconsequential amounts of water on a roof that quickly evaporate.

Bird Screen: Wire mesh installed over openings in order to prevent birds from entering a building or roof cavity.

Bitumen: Any of various flammable mixtures of hydrocarbons and other substances, occurring naturally or obtained by distillation from coal or petroleum, that are a component of asphalt and tar and are used for surfacing roads and for waterproofing.

Bituminous Emulsion: Bituminous particles suspended in water or other solution. See also Asphalt Emulsion.

Bleeder Strip: A starter strip placed along rake edges for use in asphalt shingle roofing. See also Rake-Starter.

Blind-Nailing: The use of nails so that they are not exposed to the weather in the finished roofing system.

Blister: A pocket of air trapped between layers of felt or membrane. Blisters are usually caused by water or other foreign substances.

Blocking: Pieces of wood built into a roof assembly used to stiffen the deck around an opening, support a curb, or for use as a nailer for attachment of membranes or flashing.

Blue prints: Architectural plans for a building or construction project.

Bond: The force(s) holding two components in positive contact.

Bonding Agent: A chemical agent used to create a bond between two layers.

Boot: A piece of material preformed to protect roof penetrations from dirt, moisture and other foreign and/or damaging substances.

Bow (Warp): A curve, bend or deviation from being flat.

Bridging: When membrane is unsupported at a juncture.

British Thermal Unit (BTU): The heat energy necessary to raise the temperature of one pound of water one degree Fahrenheit, a joule.

Buckle: A long, tented displacement of a roof membrane. Can occur over insulation and deck joints.

Built-Up Roof Membrane: A roof membrane consisting of layers of bitumen, which serves as the waterproofing component, with plies of reinforcement fabric installed between each layer. The reinforcement material can consist of bitumen-saturated felt, coated felt, polyester felt or other fabrics. A surfacing is generally applied and can be asphalt, aggregate, emulsion or a granule-surfaced cap sheet.

Butt Joint: Where two separate, adjacent pieces of material abut.

Butterfly roof: A roof with two opposing pitches meeting in the middle

Butyl: A hydrocarbon radical, C₄H₉. Butyl has a rubber-like consistency, is formed from the copolymerisation of isobutylene and isoprene and is used primarily in sealants and adhesives.

Butyl Rubber: A butyl-based, synthetic elastomer.

Butyl Tape: A sealant tape used in numerous sealant applications such as sealing sheet metal joints.

Although these pages are checked regularly and every care is taken with the information within. Delston can not accept any responsibility or liability for information or results displayed within due to third party interference.

Author Myrddin
Copyright © 1999 [Delston ]. All rights reserved.

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