MANSARD ROOF- A roof which rises by inclined planes from all four sides of a building.
MASTIC- A heavy trowel applied bitumen used for flashings or patch work which remains elastic and pliable.
MELT POINT- The temperature at which the solid asphalt becomes a liquid.
MEMBRANE- A generic term relating to a variety of sheet goods used for certain built-up roofing repairs and application. Also used to describe the combination of felts and moppings of bitumen forming a single flexible unit and waterproofing system of a BUR.
METAL EDGE- Brake metal or metal extrusions which are secured at the perimeter of a roof to form a weathertight seal.
MIL THICKNESS- Measurement used to determine thickness of a coating. 1 mil = .001 inch (1/1000).
MILDEW- A superficial coating or discoloration of organic materials caused by fungi, especially under damp conditions.
MINERAL SPIRITS- A by-product of petroleum, clear in color, a solvent for asphaltic coatings.
MINERAL SURFACED- A heavy roofing felt that has very small granules embedded across its surface.
MITER- The joint made by two diagonally cut pieces put together.
MODIFIED BITUMEN- Bitumen modified by special processing, generally with the addition of SBS type rubber or atactic polypylenes (APP). Some are non-reinforced, while others are reinforced with polyester, polyvinyl acetate, fiberglass, polypropylene or aluminum foil.
MOISTURE RELIEF VENT- A vent installed through the roofing membrane to relieve moisture vapor pressure that has been trapped within the roofing system. Moisture relief vents are usually installed when a new roofing system is installed above an old, failed, system.
MOISTURE SCAN- A survey of a roof specifically to detect the amount of moisture present in the roof system. Devices used in moisture surveys can be capacitance meters, infrared cameras, and nuclear scanners. Infrared scans can be done from the air or on the surface of the roof. Capacitance and nuclear scans are done on the roof surface. It is argued that the most accurate scans are done from the surface of the roof with the most accurate of these being nuclear scans.
MONITOR- A large structure rising above the surrounding roof planes, designed to give light and/or ventilation to the building interior.
MONITOR, SAW-TOOTH- A type of monitor characterized by sharp angled pitches and vertical sections, usually arranged in rows much like teeth of a saw.
MONOLITHIC- Used to describe something without seams; formed from a single material.
MONOMER- A simple molecule that can combine with other to form a polymer.
MOPPING- A layer of hot bitumen mopped between plies of roofing felt.
MOPPING, FULL- The application of bitumen by mopping in such a manner that the surface being mopped is entirely coated with a reasonably uniform coating.
MOPPING, SPOT- The procedure of applying hot bitumen in a random fashion of small daubs, as compared to full mopping.
MOPPING, SPRINKLE- A special application of installing insulation to the decks. It is done by dipping a roof mop into hot bitumen and sprinkling the material onto the deck.
MOPPING, STRIP- The application of bitumen in parallel bands.
MORTAR- Mixture of sand, mortar, limestone and water used in bonding a chimney's bricks together.
MUD CRACKS- Cracks developing from the normal shrinkage of an emulsion coating when applied too heavily and not reinforced.
NAILER- A piece of lumber secured to non-nailable decks and walls by bolts or other means, which provides a suitable backing onto which roof components may be mechanically fastened.
NAIL-GUIDE LINE- Painted line on laminated shingles, to aid in the proper placement of fasteners.
NAIL-POP- When a nail is not fully driven, it sits up off the roof deck.
NEOPRENE- A synthetic rubber produced by polymerization of Chloroprene for use in liquid-applied and sheet-applied elastomeric roofing.
NESTING- Installing a second layer of shingles aligning courses with the original roof to avoid shingle cupping.
NET FREE VENT AREA (Net Free Air Flow)- The area permitting unrestricted airflow.
NIGHT SEAL- To temporarily seal the edge of a roof membrane in order to protect it from moisture entry. A.K.A. Night Tie-Off and Water Cut-Off.
NON-DESTRUCTIVE- A phrase describing a method of examining the interior of a component whereby no damage is done to the component itself.
NUCLEAR METER- A device used to detect moisture by measuring slowed, deflected neutrons.
NRCA- National Roofing Contractors Association.
NRG- National Roof Group
OIL-CANNING- The term describing distortion of thin-gauge metal panels which are fastened in a manner restricting normal thermal movement.
OPEN VALLEY- A valley where both sides of the roof are trimmed back from the centerline to expose the valley flashing material beneath.
ORGANIC- A term designating any chemical compound which contains carbon and hydrogen.
ORGANIC FELT- An asphalt roofing base material manufactured from cellulose fibers. Organic felt has been modernly replaced with fiberglass felt.
ORGANIC MAT- Material made from recycled wood pulp and paper.
ORGANIC SHINGLE- An asphalt shingle reinforced with organic material manufactured from cellulose fibers.
OSB- Oriented Strand Board. A decking made from wood chips and
OVER-DRIVEN- The term used for fasteners driven through roofing material with too much force, breaking the material.
OVER-EXPOSED- Installing shingle courses higher than their intended
OVERHANG- That part of the roof structure which extends horizontally beyond the vertical plane of the exterior walls of a building.
OXIDIZE- To combine with oxygen in the air.