Term Description

Unit of length measurement in the SI system; 1 meter is equal to 39.37 inches.

Methylene diphenyl diisocynate (MDI)

The "A-component" (A-side) in spray polyurethane foam. An organic chemical compound having two reactive isocyanate groups. It is mixed with the "B-component" to form polyurethane in a chemical reaction.


A unit of measure, one mil is equal to 0.001 inches; often used to indicate the thickness of a roof membrane.


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


A unit of measure equal to one thousandth (0.001) of a meter, or 0.03937 inches.

Mineral granules

See "granules."

Mineral stabilizer

A fine, water-insoluble inorganic material used in a mixture with solid or semisolid bituminous materials.

Mineral-surfaced roofing

Roofing materials with a surface or top layer consisting of a granule-surfaced sheet.

Model (building) codes

A compilation of standards or codes established to provide uniformity in regulations pertaining to building construction.

Modified bitumen

See "polymer-modified bitumen."

Moisture-retention layer

Commonly, an absorptive mat consisting of recycled polypropylene fibers that retains or stores moisture for plant growth.


A surface growth of fungus on damp or decaying matter. The term has no taxonomic significance and is used only in a general sense of visible fungal growth on organic matter. See "mildew."


Formed from or composed of a single material; seamless.


A low-molecular-weight substance consisting of molecules capable of reacting with like or unlike molecules to form a polymer.

Mop and flop

An application procedure in which roofing elements (insulation boards, felt plies, cap sheets, etc.) are initially placed upside down adjacent to their ultimate locations; coated with adhesive or bitumen; and turned over and adhered to the substrate.


The application of hot bitumen with a mop or mechanical applicator to the substrate or plies of a bituminous membrane. There are two types of mopping as follows:
mopping, solid: A continuous coating

mopping, spot: Bitumen is applied roughly in circular areas, leaving a grid of unmopped perpendicular areas


See ‚"safety data sheet (SDS).‚"


North American Fiberboard Association


National Association of Home Builders.


(Sometimes referred to as "blocking"); a piece or pieces of dimensional lumber and/or plywood secured to a structural deck or walls that provides a receiving medium for the fasteners used to attach membrane or flashing. See "blocking (1)."

Nailing strips

A member, usually of wood, set into or secured to nonnailable roof decks or walls to allow for positive anchorage by nailing of roofing felts, insulation or flashings.


Acrylonitrile butadiene polymer blend. One proprietary NBP membrane is commonly referred to as nitrile-butadiene copolymer.


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


(1) The installation of new metal roof deck directly on top of existing metal roof deck; (2) a method of reroofing with new asphalt shingles over existing shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle; also known as "butt-and-run method."

Newton (N)

SI unit of measure for force.