Roofing Glossary: M to P

M

Mastic

Caulking or sealant normally used in sealing roof panel laps.

Membrane

A flexible or semi-flexible roof covering or waterproofing layer, whose primary function is the exclusion of water.

Mildew

a superficial growth produced on organic matter or living plants by fungi.

Modified Bitumen

a bitumen modified by including one or more polymers (e.g., atactic polypropylene, styrene butadiene styrene, etc.);
composite sheets consisting of a polymer modified bitumen often reinforced with various types of mats or films and sometimes surfaced with films, foils or mineral granules.

Mop-and-Flop

A procedure in which roof components (insulation boards, felt plies, cap sheets, etc.), are initially placed upside down adjacent to their ultimate locations, are coated with adhesive, and are then turned over and adhered to the substrate.

Mopping

an application of hot bitumen applied to the substrate or to the felts of a built up roof membrane with a mop or mechanical applicator.

N

Nailing

In the EXPOSED NAIL METHOD, nail heads are exposed to the weather;
In the CONCEALED NAIL METHOD, nail heads are concealed from the weather

Neoprene

a synthetic rubber (polychloroprene) used in liquid and sheet-applied elastomeric roof membranes or flashings.

O

Overhang

a roof extension beyond the exterior wall of a building.

P

Pallets

a platform (typically wooden) used for storing and shipping materials.

Pan

the bottom flat part of a roofing panel that is between the ribs of the panel.

Panel Clip

Independent clip used to attach roof panels to substructure.

Panel Creep

Tendency of the transverse dimension of a roof panel to gain in modularity due to spring-out or storage-distortion.

Parapet

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

Penetration

any construction (e.g., pipes, conduits, HVAC supports) passing through the roof;
the consistency of a bituminous material expressed as the distance, in tenths of a millimeter (0.1 mm), that a standard needle penetrates vertically into a sample of material under specified conditions of loading, time, and temperature.

Perlite

an aggregate used in lightweight insulating concrete and preformed perlitic insulation boards, formed by heating and expanding siliceous volcanic glass.

Permeance

the rate of water vapor transmission per unit area at a steady state through a material, membrane, or assembly;
the time rate of water vapor transmission through unit area of flat material or construction induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. The English (inch•pound) unit of measurement for permeance is gr/h•ft2•in. Hg, which is commonly referred to as “perm” units.

Phasing

The installation of a roof system or waterproofing system during two or more separate time intervals

Pig spout

A sheet metal flashing designed to direct the flow of water out through the face of the gutter rather than through a downspout.

Pitch

See Incline

Pitch Pocket

A flanged, open-bottomed, metal container placed around columns or other roof penetrations that is filled with hot bitumen and/or flashing cement to seal the joint.

Ply

a layer of felt or ply sheet in a built-up roof membrane or roof system.

Pond

A roof area that retains water instead of draining after rainfall.

Primer

a thin, liquid-applied solvent-based bitumen that may be applied to a surface to improve the adhesion of subsequent applications of bitumen;
a material that is sometimes used in the process of seaming single-ply membranes to prepare the surfaces and increase the strength (in shear and peel) of the field splice;
a thin liquid applied material that may be applied to the surface of SPVF to improve the adhesion of subsequent application of SPVF protective coatings.

Protected Membrane Roof

Roof assembly with insulation on top of membrane instead of vice versa, as in conventional roof assembly (also known as inverted or upside-down roof assembly).