Macromolecule—A large molecule in which there is a large number of one or several relatively simple structural units, each consisting of several atoms bonded together.

Maintenance and repair cost—the total of labor, material, and other related costs incurred in conducting corrective and preven-tative maintenance and repair on a building, or on its systems and components, or on both.

Masonry—Anything constructed of materials such as bricks, concrete blocks, ceramic blocks, and concrete.
Mastic—Caulking or sealant normally used in sealing roof panel laps.

Matte finish—A dull finish produced by rolling sheet steel on specially prepared rolls.

Membrane—A flexible or semiflexible roof covering or waterproofing whose primary function is the exclusion of water.

Memory—Tendency of a material to regain a previous configuration—notably, the tendency of glass-fiber felts not to lie flat on their substrate after unrolling; the retraction of single-ply roll goods which were stretched during production or winding.

Mer—The repeating of structural unit of any high polymer.

Mesh—The square opening of a sieve.

Metal flashing—See Flashing—Frequently used as through-wall cap, or counter-flashing.

Metallurgical compatibility—The tendency of certain heavy metals to react electrochemically with aluminum.

Microns—(Also called micrometers). A unit of measurement equal to 10* meters (.000001 meters) or 10,000 Angstrom units.
Mineral fiber—Inorganic fibers of glass, asbestos or mineral wool (slag).

Mineral fiber felt—A felt with rock wool as the principle component.

Mineral granules—Natural or synthetic aggregate, ranging in size from 500|im (l^m = I0*m) to 1/4 in. diameter, used to surface BUR or modified bitumen cap sheets, asphalt shingles, and some cold process membranes.

Minimum detectable temperature difference—A quantification of the smallest temperature difference which may be discerned between one point and another on an object using an infrared sensor.

Model codes—Codes established to provide uniformity in regulations pertaining to building construction. Examples:
Uniform Building Code published by ICBO
National Building Code by BOCA
Standard Building Code by SBCCI

Modulus of elasticity—The ratio of stress (nominal) to corresponding strain below the proportional limit of a material. It is expressed in force per unit area based on the minimum initial cross sectional area.

Moisture conduction—Migration by wicking as contrasted to vapor movement.

Moisture contour map—A map with lines connecting continuous levels of moisture. When drawn by computer the wettest areas are often indicated by darkest symbols and the driest areas left blank.

Mole run—A meandering ridge in a membrane not associated with insulation or deck joints.

Monochrome image (grey image)—A thermal image with a blending of grey tones from dark to light but without the presence of isotherms.

Monolithic construction—A method of pouring concrete grade beam and floor slab together to form the building foundation without forming and pouring each separately.

Monomer—A simple molecule which is capable of combining with a number of like or unlike molecules to form a polymer.

Mop-and-flop—A procedure in which roofing elements (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—The application of hot bitumen with a mop or mechanical applicator to the substrate or to the plies of a built-up roof. There are four types of mopping: (1) solid—a continuous coating; (2) spot—bitumen is applied in roughly circular areas, generally about 460 mm (18 in.) in diameter, leaving a grid of unmopped, perpendicular area, (3) strip—bitumen is applied in parallel bands, generally 200 mm (8 in.) wide and 300 mm (12 in) apart; (4) sprinkle—bitumen is shaken on the substrate from a broom or mop in a random pattern.

Mud cracking—Surface cracking resembling a dried mud flat.