Material safety data sheets (MSDS): written descriptions of the chemicals in a product provided by the product’s manufacturer. MSDS also contain other information such as emergency procedures and safe handling.
Mastic: a thick adhesive material used as a cementing agent for holding waterproofing membrane in place
Mat: a thin layer of woven, non-woven, or knitted fiber that serves as reinforcement to a material or membrane.
Mechanical fasteners: devices such as screws, plates, battens, nails, or other materials that are used to secure roofing materials.
Mechanically fastened membranes: generally used to describe membranes that have been attached at defined intervals to the substrate.
Membrane: a flexible or semi-flexible roof covering or waterproofing whose primary function is to exclude water.
Metal flashing: roof components made from sheet metal that is used to terminate the roofing membrane or material along roof edges. Metal flashings are also used in the field of the roof around penetrations.
Mil: a unit of measure equal to 0.001 inches (1/1000 in.) used to indicate the thickness of a roofing membrane.
Modified bitumen: a bitumen modified by one or more polymers such as Atactic Polypropylene (APP), styrene butadiene styrene (SBS).
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.
Mud cracking: surface cracking resembling a dried mud flat.
Multiple coats: more than one layer of coating applied to a substrate.