University of California, an independent fire-testing laboratory.

Coefficient of heat transfer, "U" equals 1 divided by (hence, the reciprocal of) the total of the resistances of the various materials, air spaces and surface air films in an assembly. See Thermal Resistance.

Uniform Building Code - document promulgated by the International Conference of Building Officials.

Underwriters Laboratories Inc., founded by NBFU, and now operated in affiliation with American Insurance Assn. UL is a not for profit laboratory operated for the purpose of testing devices, systems and materials as to their relation to life, fire and casualty hazard in the interest of public safety.

The maximum stress, such as tensile, compressive, or shear, that a material can withstand.

The maximum tensile stress of a  material up to the point of rupture.

A method of non-destructive testing of materials that uses high frequency sound vibrations to find defects in the material.

A flat, insulated electric wire that is run under the carpet.

Sheet material, such as hardboard, that is laid over the subfloor to provide a smooth, stiff surface for the finish flooring.

Placing a new foundation below the existing foundation.

A neat gypsum. It has no additives.

Any load that is spread out evenly over a large area.

Concrete placed without steel-reinforcing bars or welded-wire fabric.

United States of America Standards Institute, now American National Standards Institute.