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Term Definition
Makeup Air

Air brought into a building from the outside to replace air that has been exhausted.


The property of a metal that permits it to be formed mechanically, such as by rolling or forging, without fracturing.


An access hole in a drainage system to allow inspection, cleaning, and repair.


A metamorphic rock formed largely of calcite, dolomite, or dense limestone.

Masonry Cement

A hydraulic cement used in mortars to increase plasticity and water retention.


Property of a body that resists acceleration and produces the effect of inertia. The weight of a body is the result of the pull of gravity on the body's mass.


The trademarked title of a uniform system for indexing construction specifications published by the Construction Specifications Institute and Construction Specifications Canada.


A doughlike compound available in many different formulations designed for use as sealants and adhesives.

Mat Foundation

A large, single concrete footing equal in area to the area covered by the footprint of the building.

Mechanical Action

The bonding of materials by adhesives that enter the pores and harden, forming a mechanical link.

Mechanical Properties

Properties exhibited by a material's reaction to applied forces, such as tensile strength and compressive strength.


A white crystalline made from calcium cyanamide.

Melting Temperature

The temperature at which a material turns from a solid to a liquid.


A continuous, unbroken roof covering.

Metal Lath

Perforated sheets of thin metal secured to studs that serve as the base for a finished plaster wall.

Metamorpihic Rock

Rock formed by the action of pressure and/or heat on sedimentary soil or rock.

Meter, Electric

A device measuring and recording the amount of electricity passing through it in kilowatt-hours.

Metes and Bounds

A formal description of the boundary lines of a parcel of real property in terms of the length and direction of those lines.

Metric Terms

Metric units shown as equivalents in this Handbook are from the International System of Units in use throughout the world, as established by the General Conference of Weights and Measures in 1960. Their use here complies with the Metric Conversion Act of 1975, which committed the United States to a coordinated voluntary conversion to the metric system of measurement. Refer to the Appendix for metric units and conversion factors applicable to subjects covered in this Handbook. For additional information, refer to ASTM E380-76, Standard for Metric Practice.

Mild Steel

Steel containing less than 0.3 percent carbon.


An agent that helps prevent the growth of mold and mildew on painted surfaces.


Wood interior finish items manufactured in a factory, such as doors, windows, and cabinets.


Joint formed by two pieces of material cut to meet at an angle.

Model Code

Building code, written and published by a building-official association, available to states, counties and municipalities for adoption (for a fee) in lieu of their own, e.g., Uniform Building Code, Standard Building Code, National Building Code.

Modified Bitumens

A roofing membrane composed of a polyester or fiberglass mat saturated with a polymer-modified asphalt.

Modular Size

A dimension that conforms to a given module, such as the 48-inch width of plywood panels.


(1) In architecture, a selected unit of measure used as a basis for building layout; (2) In industrialized housing, a three-dimensional section of a building, factory-built, shipped as a unit and interconnected with other modules to form the complete building. Single-family units factory-built in two halves are usually referred to as "sectionals."

Modulus of Elasticity (E)

Ratio between deformation, a measure of the stiffness of a material.

Modulus of Rupture

A measure of the ultimate load-carrying capacity of a structural member.

Moisture Barrier

A membrane used to block the passage of water, and water vapor through an assembly of materials, suh as a wall.

Moisture Content

The amount of water contained in wood expressed as a percentage of the weight of the wet wood to the weight of an oven-dry sample.


The tendency of a force to cause rotation about a give point or axis.

Moment of Inertia (I)

Calculated numerical relationship (expressed in in.4) of the resistance to bending of a member, a function of the cross-sectional shape and size. A measure of the stiffness of a member based on its shape. Larger moments of inertia indicate greater resistance to bending for a given material.

Monolythic Concrete

Concrete cast with no joints except construction joints: a continuous pour.


An organic molecule that can be converted into a polymer by chemical reaction with similar molecules or organic molecules.


A plastic mixture of cementitious materials, water, and fine aggregate.

Mortar Flow

A measure of the consistency of freshly mixed mortar related to the diameter of a molded truncated cone specimen after the sample has been vibrated a specified number of times.


A decoration made up of small pieces of inlaid stone, glass, or tile.

Motor Control

A device that governs the electric power delivered to one or more electric motors.

Motor Control Center

Controllers used to start and stop electric motors and protect them from overloads.

Moulding (also Molding)

Narrow decorative strip applied to a surface.

Moving Ramp

A conveyor belt system used to move people or packages up or down an incline.

Moving Walk

A conveyor belt system operating at floor level used to move people in a horizontal direction.


Vertical bar or division in a window frame separating two or more panes.

Multiple Dwelling

A building containing three or more dwelling units.


Horizontal bar or division in a window frame separating multiple panes or lights.

Music/Machinery Transmission Class (MTC)

Rating developed by U.S. Gypsum Company to isolate music and machinery/mechanical equipment noise or any sound with a substantial portion of low frequency energy. MTC does not replace Sound Transmission Class (STC) but complements it.

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