Abrasion Resistance: The ability of a membrane to resist abrasion caused by foot traffic, wind-blow particles, or the movement of equipment

Absorption: The ability of a material to accept quantities of gases or liquids

Adhesive: A substance used to adhere materials together

Aggregate: Any granular material including crushed stone, slag, or gravel

Alligatoring: The cracking of surface bitumen on a built-up roof resulting from expansion or contraction

Application Rate: The quantity (measured in mass, volume, or thickness) of material applied per unit area

Asphalt: A brownish-black mixture of bitumens obtained from nature or through petroleum processing


Ballast: A material such as aggregate which employs its mass and the force of gravity to hold single-ply roof membranes in place

Base Flashing: Plies or strips of roofing membrane used to seal the roof at the horizontal-to-vertical intersections

Base Ply: The bottommost ply of the roofing membrane

Base Sheet: A material used as the first ply on some low-slope systems

Batten: Cap or cover

Bitumen: A general term for a semi-solid mixture of hydrocarbons

Blister: A raised portion of the roofing membrane resulting from pressure buildup caused by trapped gases in the membrane

Blocking: The wood between the deck and the membrane

Buckling: Warping or wrinkling of the roof membrane


Cant Strip: A beveled strip of wood used under flashings to modify the point at which the roofing or waterproofing membrane meets any vertical element

Cap Sheet: A granule-surfaced felt that is used as the top ply of a built-up roofing membrane

Caulking: A waterproofing sealant used for filling joints

Color Stability: A property of a material to retain its original color after environmental exposure

Compressive Strength: A property of a material to resist deformation caused by compression

Condensation: As it relates to water, the conversion of water vapor to a liquid as the temperature drops

Condensation: As it relates to water, the conversion of water vapor to a liquid as the temperature drops

Coping: The covering on top of a wall that is exposed to weather

Counterflashing: Metal or elastomeric sheeting secured on or into a wall, curb, pipe, rooftop unit, or other surface to protect the upper edge of the base flashing

Creep: The gradual movement of a roofing membrane caused by mechanical loading or gravity

Cricket: A small, elevated area used to divert water from a horizontal intersection of the roof with a chimney, wall, expansion joint or other projection

Curb: A raised member used to support roof penetrations

Cure: A process where the material forms a permanent molecular bond after being exposed to a chemicals, heat, or pressure


Dead Level: Absolute horizontal; no slope, flat

Deck: The structural component of the roof of a building to which the waterproofing system is applied

Delamination: Separation of the roofing plies

Dimensional Stability: The change in a material that results from exposure to elevated temperature

Downspout: A vertical pipe for draining water from roof gutters

Drain: An outlet designed to capture or direct the flow of water from a roof

Drip Edge: A metal flashing or other overhanding component intended to control the direction of dripping water


Edge Stripping: Membrane flashing strips used to cover a joint between flashing and built-up roofing

Elastomeric: The elastic rubber-like properties of a material

Elongation: The ability of a roofing material to be stretch by the application of force

Embrittlement: The loss of flexibility, elasticity, or ductility of a material

Exhaust Ventilation: Air that is vented from the roof cavity

Expansion Joint: A structural separation between two building elements that allows for free movement between the elements to the roofing or waterproofing system


Fabric: A woven cloth composed of filaments, threads or yarns and used to reinforce certain membranes

Fasteners: A wide array of mechanical fastening devices including clips, screws, or bolts

Felt: A fabric manufactured from vegetable, asbestos, or glass fibers in the presence of mechanical work, moisture or heat

Field Seam: A splice or seam made in the field where overlapping sheets are joined together using an adhesive, splicing tape or heat/solvent welding

Fishmouth: A membrane defect caused by wrinkling or shifting of ply sheets; edge wrinkle

Flaking: Detachment of small pieces of the coating

Flashing: Weatherproofing components used to seal roof system edges at perimeters, walls, expansion joints, valleys, drains, and other places

Flood Test: Testing procedure using a controlled amount of water to determine the effectiveness of the waterproofing system


Gauge: A metal thickness measurement

Granule: Aggregate commonly used to surface cap sheets, shingles, and other surfaced roof coverings

Gravel: Coarse, granular aggregate used in a bitumen aggregate on built-up roofs

Gutter: A channeled component used to contain water runoff from the roof to the downspouts


Heat Welding: Method of melting or fusing together sheets of thermoplastic and polymer modified bitumen

Hem: Edge created by folding metal back on itself

Hoist: Lifting device

HVAC: Heating, ventilating, and air conditioning equipment


Ice Dam: A mass of ice formed near transitions from warm to cold roof surfaces

Infrared Thermography: Roof analysis technique used to measure the temperature gradient of a roof surface to locate areas of moisture

Insulation: Materials used to reduce the flow of heat

Intake Ventilation: Ventilation system that allows for the flow of fresh air into the building


Joist: Timber, metal or wooden beams arranged parallel to each other to support a floor or ceiling


Laminate: To join layers of material together via heat and/or pressure

Lap: The part of a roofing membrane that covers any portion of another section of membrane and is then sealed to form a watertight connect

Low-slope roofs: A category of roofs that have a slope at or less than 3:12 (14 degrees)


Mastic: Adhesive material used as a cementing agent for securing waterproofing membrane

Mat: A thin layer of fiber which reinforces the membrane

Mechanically fastened membrane: Membranes that have been attached at defined intervals to the substrate using fasteners or other mechanical devices

Membrane: A flexible or semi-flexible sheet of thermoset, thermoplastic, or modified bituminous material whose primary function is waterproofing

Modified Bitumen: A bitumen modified by one or more polymers

Mopping: The application of hot bitumen with a mop to the substrate of a bituminous membrane


Nailer: A piece of dimensional lumber or plywood which serves as a receiving medium for the fasteners

Night Seal: A temporary seal used during construction to protect the roofing assembly from water penetration


Open time: The period of time after an adhesive has been applied and an effective bond can be achieved by joining two surfaces

Overflow Drainage: Component of a roof drainage system that protects the roof against damage in the event that the primary drainage system is blocked

Ozone Resistance: A property of a material to resist the effects of ozone exposure


Parapet Wall: Perimeter wall that extends above the roof surface

Partially Attached: A method of roofing assembly in which the membrane has been spot affixed to a substrate using an adhesive or mechanical device

Penetration: Any element (e.g., pipes, conduits, HVAC supports) that pass through the roof

Pigment: A compound used to impart color

Pinhole: A tiny hole in the roof coating, film, foil, membrane or laminate components

Pipe Boot: Pre-fabrications flashing component used to flash around a circular penetration

Pitch Pocket: A flange, open-bottomed metal enclosure placed around a penetration and filled with hot bitumen or flashing cement

Ply: A layer of felt in a built-up roof system

Pond: A surface which is incompletely drained

Positive Drainage: Drainage condition in which all considerations during the design process have been provided to ensure drainage of the roof within 48 hours

Pourable Sealer: A two-part sealer used at difficult-to-flash penetrations

Primer: A substance intended to prepare the roof surface for accepting a coating or improving the overall adhesion of the coating to the substrate

Protection Mat: A mat used to shield or protect one roof system component from another


Re-covering: The process of covering an existing roof system with a new system

Reflectivity: The ability of a material to reflect light and heat

Reinforced Membrane: A membrane reinforced with felts, mats, fabrics, or other fibers

Roof Curb: A raised frame used to mount mechanical units on the roof

Rubber: A material, at room temperatures, is capable of recovering substantially in shape and size from large deformations


Scupper: A drainage component consisting of an outlet through a wall, parapet wall, or raised roof edge lined with a soldered sheet metal sleeve

Sealant: A material that is used as an adhesive to form a seal

Sealant Backing: A material place in a joint before applying sealant

Seam: A joint formed by joining two separate sections of material

Self-Adhering Membrane: A membrane that adheres to the substrate and overlaps without the use of additional adhesive

Shrinkage: A decrease in one or more dimensions of an object

Single-ply membranes: Roof membranes that are applied using just one layer of membrane material

Skylight: An opening in the roof that is glazed with a transparent or translucent material that allows light to diffuse into the space below

Snow load: The load due to the weight of the snow on a roof

Soffit: The exposed undersurface of any exterior overhanging section of a roof eave

Solvent: Any liquid used to dissolve another material

Splice: Joining of overlapping materials

Split: A tear in the membrane resulting from tensile stresses

Steep-Slope Roofs: A category of roofing systems installed on slopes greater than 3:12 (14 degrees)

Surfacing: The top layer of a roof covering


Tear Resistance: The load required to tear a material when the stress is concentration on a small area of the specimen by the introduction of a prescribed flaw

Termination: A method of anchoring the free edges of the membrane to the roofing system

Thermoplastic: A material that softens when heated and hardens when cooled


Ultraviolent: A form of radiation that is potentially damaging to certain chemical compounds in the roofing membrane


Vapor Retarder: Material installed to restrict the flow of water vapor through the roofing assembly

Vegetative Roofs: A roof system composed of a waterproof substrate and an area of planting


Water Absorption: The amount of water absorbed by a material within a specific period of time

Waterproof: A property of a material to resist water

Weep Holes: Small holes whose purpose is to permit drainage of water that accumulates inside a building component

Weld: Joining of metal together by heat fusion