Machine Stress Rated Lumber (MSR Lumber) assures the performance and reliability of your engineered components and structures.The machine grading process sorts dimension lumber by strength and stiffness to improve consistency.

Main Breaker - 1. A switch in a main electrical service panel where the service wires attaches. 2. The main electrical service protective device where the power enters a building.

Mansard Roof - Roof style with four sides similar to a hip roof but each side is divided into an upper and lower section, the lower section having a steeper slope than the upper section. Often, the center of the mansard roof consists of a flat roof.

Mantel - The shelf above a fireplace opening. Also used in referring to the decorative trim around a fireplace opening.

Manufactured Wood - A wood product such as a truss, beam, gluelam, microlam or joist which is manufactured out of smaller wood pieces and glued or mechanically fastened to form a larger piece. Often used to create a stronger member which may use less wood. See also Oriented Strand Board.

Manufacturer's Specifications - The written installation and/or maintenance instructions which are developed by the manufacturer of a product and which may have to be followed in order to maintain the product warranty.

Masonry - Stone, brick, concrete, hollow-tile, concrete block, or other similar building units or materials. Normally bonded together with mortar to form a wall.

Mastic - A pasty material used as a cement (as for setting tile) or a protective coating (as for thermal insulation or waterproofing)

MDF (Medium Density Fiberboard) - Type of pressed fiberboard often used in cabinet building and baseboards.

Mechanical Systems - The heating, cooling, plumbing, and electrical systems within a house or building.

Mechanics Lien - A lien on real property, created by statue in many years, in favor of persons supplying labor or materials for a building or structure, for the value of labor or materials supplied by them. In some jurisdictions, a mechanics lien also exists for the value of professional services. Clear title to the property cannot be obtained until the claim for the labor, materials, or professional services is settled. Timely filing is essential to support the encumbrance, and prescribed filing dates vary by jurisdiction.

Membrane - A flexible or semi-flexible material, which functions as the waterproofing component in a roofing or waterproofing assembly, and whose primary function is the exclusion of water.

Mesh - Welded steel used for concrete reinforcement

Metal Lath - Sheets of metal that are slit to form openings within the lath. Used as a plaster base for walls and ceilings and as reinforcing over other forms of plaster base.

Mezzanine - An intermediate floor assembly between the floor and ceiling of any room or story and includes an interior balcony.

Microlam - A manufactured structural wood beam. It is constructed of pressure and adhesive bonded wood strands of wood. They have a higher strength rating than solid sawn lumber. Normally comes in l ½" thickness' and 9 ½", 11 ½" and 14" widths.

Milar (Mylar) - Plastic, transparent copies of a blueprint.

Millwork - Generally all building materials made of finished wood and manufactured in millwork plants. Includes all doors, window and door frames, blinds, mantels, panelwork, stairway components (ballusters, rail, etc.), mouldings, and interior trim. Does not include flooring, ceiling, or siding.

Mineral Wool – A material used for insulating buildings, produced by sending a blast of steam through molten slag or rock: common types now in use include, rock wool, glass wool, and slag wool.

Miter - An angled cut, usually 45°. Unlike a compound miter cut, the saw blade remains straight at 0°.

Miter Joint - The joint of two pieces at an angle that bisects the joining angle. For example, the miter joint at the side and head casing at a door opening is made at a 45° angle.

Modular Construction - Construction in which the size of the building and the building materials are based on a common unit of measure.

Monolithic - Term used for concrete work poured and cast in one piece without joints.

Monopost -are  columns made up of steel cylinders topped by a couple of steel plates joined by a large threaded rod. This threaded rod allows the overall height of the Jack Post assembly to be adjusted by turning the rod. Jack Posts are installed underneath the beams that support floor joists, which make them an integral part of the floor structure. (See Telepost & Jack Post)

Mono Truss - Truss that has only one slope so that its outline is a triangle. Generally installed to rest on an exterior wall and on an inside bearing wall or they will bear on the vertical member at the high end of the truss. Mono trusses may be used to form the outside portion of a mansard roof.

Mortar - A mixture of cement (or lime) with sand and water used in masonry work.

Mortar Bed – Layer of mortar on which any structural member, masonry unit, or tile is bedded.

Mortgage - Loan secured by land.

Mortgage Broker - A broker who represents numerous lenders and helps consumers find affordable mortgages; the broker charges a fee only if the consumer finds a loan.

Mortgage Company - A company that borrows money from a bank, lends it to consumers to buy homes, then sells the loans to investors.

Mortgage Deed - Legal document establishing a loan on property.

Mortgagee - The lender who makes the mortgage loan.

Mortgage Loan - A contract in which the borrower's property is pledged as collateral. It is repaid in installments. The mortgagor (buyer) promises to repay principal and interest, keep the home insured, pay all taxes and keep the property in good condition.

Mortgage Origination Fee - A charge for work involved in preparing and servicing a mortgage application (usually one percent of the loan amount).

Mortise - A slot cut into a board, plank, or timber, usually edgewise, to receive the tenon (or tongue) of another board, plank, or timber to form a joint.

Moulding - A wood strip having an engraved, decorative surface.

Mud Room - A small room or entranceway where muddy overshoes and wet garments can be removed before entering other rooms.

Mudsill - Bottom horizontal member of an exterior wall frame which rests on top a foundation, sometimes called sill plate. Also sole plate, bottom member of interior wall frame.

Mulch - A natural substances made of leaves, straw and earth.

Mullion - A vertical divider in the frame between windows, doors, or other openings.

Muntin - A small member which divides the glass or openings of sash or doors.

Muriatic Acid - Commonly used as a brick cleaner after masonry work is completed.

Mushroom - The unacceptable occurrence when the top of a caisson concrete pier spreads out and hardens to become wider than the foundation wall thickness.