Atactic Polypropylene (APP): 

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

 

Blister: 

An enclosed pocket of air which may be mixed with water or solvent vapour trapped between the impermeable layers of felt or membrane or between the membrane and primed substrate.

 

Bond: 

The adhesive and/or cohesive forces holding two components in positive contact.

 

Butt Joint: 

A joint or seam formed by joining separate sections of a membrane at the edge without overlapping (i.e. edge to edge). Once the edges have been joined the seam is usually covered and sealed with a narrow strip of membrane material or compatible tape.

 

Cant Strip: 

A bevelled or triangular-shaped strip of wood, wood-fibres, perlite, or other material (sand-cement) designed to serve as a gradual transitional plane between the horizontal surface of a roof deck or rigid insulation and a vertical surface.

 

Fillet: 

Similar to a cant strip made of preformed plastic, wood or made in-situ by sand-cement, generally installed at the point where vertical and horizontal surfaces meet; the desired effect to take out the 90° angle at the base of a vertical flashing.

 

Fish mouth: 

A half-cylindrical or half-conical shaped opening or void in a lapped edge or seam, usually caused by wrinkling or shifting of ply sheets during installation, or irregular welding where proper alignment has not been observed.

 

Flash Point:

The lowest temperature of a liquid at which it gives off vapours sufficient to form an ignitable mixture with the air near its surface.

 

Gravel: 

Aggregate resulting from the natural erosion of rock.

 

Heat Welding: 

It is a process or method of melting and sealing or fusing together the overlapping edges of separate sections of thermoplastic or uncured elastomeric roofing membranes, by the application of heat and pressure.

 

Loose-Laid Membrane:

A ballasted single ply roofing membrane that is attached to the substrate only at the building edges and penetrations through the roof. Modified bitumen membrane should be fully bonded to the substrate at 1 meter from either end and at all upstands or vertical surfaces.

 

Non-Woven: 

A term used to describe the random arrangement of reinforcing fibres (glass, polyester etc.) in a mat or scrim.

 

Peel Strength: 

The average force (or force per unit width) required to peel a membrane or other material from the substrate to which it has been bonded.

 

Penetration: 

The consistency (hardness) of a bituminous material expressed as the distance in tenths of a millimetre (0.1 mm) that a standard needle penetrates vertically into a sample of material under specified conditions of loading, time and temperature.

 

Permeability: 

The capacity of a porous material to conduct or transmit fluids.

The amount of a fluid moving through a barrier in a unit time, unit area, and unit pressure gradient not normalized for but directly related to the thickness.

Plastomeric: 

A plastic-like polymer consisting of any of various complex organic compounds produced by polymerization and capable of being moulded, extruded or cast into various shapes or films.

 

Ponding: 

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

 

Primer: 

Thin, liquid, solvent-based bitumen that may be applied to a porous surface to improve the adhesion of bituminous waterproofing membranes to substrates .

 

Protected Membrane Roof (PMR): 

An insulated and ballasted roofing assembly in which the insulation and ballast are applied on top of the membrane.

 

Seam: 

A joint formed by fusion of two separate sections of a single ply roofing membrane. Seams may be sealed in a variety of ways including torching, hot-air welding and adhesive bonding.

 

Selvage: 

An edge or edging that differs from the main part of fabric, granule surfaced roll roofing or cap- sheet, or other material 

A specially defined edge of the material (lined for demarcation), which is designed for some special purpose such as overlapping or seaming.

Service Temperature Limits: 

The minimum or maximum temperature at which a coating or other material will perform satisfactorily.

 

Side Lap: 

The continuous longitudinal edge of neighbouring like materials.

 

Softening Point:

The temperature at which asphalt becomes soft enough to flow as determined by a closely defined test method.

 

Tear Resistance: 

The load required to tear a material when the stress is concentrated on a small area of the specimen by the introduction of a prescribed flaw. It's expressed in Newton or pounds per linear cm or inch.

 

Tensile Strength:

The maximum force (longitudinal pulling stress) a material can bear without tearing or breaking apart.

 

Thermal Insulation: 

A material applied to reduce the flow of heat.

 

Ultraviolet (UV): 

Situated beyond the visible spectrum, just beyond the violet end, having wavelengths shorter than wavelengths of visible light and longer than those of X-rays.

 

Water Absorption: 

The amount of water absorbed by a material after being immersed for a prescribed period of time. It may be expressed as a percentage of the original weight of the material.

 

Water Vapour Transmission: 

A measure of the rate of transmission of water vapour through a material under controlled laboratory conditions of temperature and humidity.

 

Customary units are grains/h ~ ft ². (See ASTM Standard E 96).