Search for glossary terms (regular expression allowed)
Term Definition
Nail Pop

The protrusion of the nail usually attributed to the shrinkage of or use of improperly cured wood framing.

Nail Popping

The loosening of nails holding gypsum board to a wall or ceiling. It produces a bulge in the surface of the gypsum panel.

Natural Fibers

Fibers found in nature, such as wool and cotton.


National Board of Fire Underwriters, now merged into the American Insurance Assn.


National Bureau of Standards, a federal agency.


National Conference of States on Building Codes and Standards, a nonprofit organization formed to increase interstate cooperation and coordinate intergovernmental reforms of building codes.

Neat Plaster

A gypsum plaster with no aggregates or fillers added. Sometimes called unfibered gypsum.

Needle Beam

A steel or wood beam that is run through an opening in a bearing wall and used to support the wall and related loads as work on the foundation below the wall is performed.

Neutral Axis

The plane through a member (at the geometric center of the section in symmetrical members) where the fibers are neither under tensile nor compressive stress.


National Fire Protection Assn., an international technical society that disseminates fire prevention, fighting and protection information. NFiPA technical standards include the National Electrical Code which is widely adopted.


National Forest Products Association.

Noise Reduction Coefficient (NRC)

A single number indicated by the amount of airborne sound energy absorbed into a material. The arithmetic average of sound absorption coefficients at 250, 500, 1000 and 2000 Hz.


Term indicating that the full measurement is not used; usually slightly less than the full net measurement, as with 2" x 4" studs that have an actual size when dry of 1&1/2" x 3&1/2".

Non-Conforming Use

A particular use of land or a structure which is in violation of the applicable zoning code. Generally, if the use was established prior to the code rule which it contravenes, it may continue to exist.


Refers to a structural part that does not carry a load.

Noncalcerous Clays

Clays containing silicate of alumina, feldspar, and iron oxide.


Definition excerpted from the ICBO Uniform Building Code: 1. Material of which no part will ignite and burn when subjected to fire. 2. Material having a structural base of noncombustible material as defined, with a surface not over 1/8" thick that has a flame spread rating of 50 or less. The term does not apply to surface finish materials.

Nondestructive Testing

Methods of testing an item that do not destroy the item being tested.


Metallic materials in which iron is not a principal element.

Nonheat-Treatable Alloys

Alloys that do not increase in strength when they are heat treated but that do gain strength by the addition of alloying elements.

Nonprestressed Units

Concrete structural members in which the reinforcing steel is not subject to prestressing or post-tensioning.


A synthetic plastic made from coal, tar, and water.

blank spacer