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.

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.

An independent testing agency that checks electrical devices and other components for possible safety hazards.

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

University of California, an independent fire-testing laboratory.

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

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

Products with a ULEF certification have ultra-low emitting formaldehyde resins which have been shown to have formaldehyde emissions below the limits established by CARB Phase 2. The ULEF certification originated with CARB, and has since been adopted by the EPA for the TSCA Title VI regulation. https://healthymaterialslab.org/tool-guides/hml-resources

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

A ¼" material placed over the subfloor plywood sheeting and under finish coverings, such as vinyl flooring, to provide a smooth, even surface. Also a secondary roofing layer that is waterproof or water-resistant, installed on the roof deck and beneath shingles or other roof-finishing layer.

Placing a new foundation below the existing foundation.

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

A plumbing fitting that joins pipes end-to-end so they can be dismantled.

A coating applied prior to the finishing or top coats of a paint job. It may be the first of two or the second of three coats. Sometimes called the Prime coat.

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

The plumbing drain and waste lines that are installed beneath a basement floor.

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

A neat gypsum. It has no additives.

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

Formaldehyde is classified by the International Agency for Research on Cancer and the State of California as a known human carcinogen. Common health effects at low levels of exposure to this volatile organic compound include irritation and sensitization as well as acting as an asthma trigger. Long-term exposure is associated with nasal cancers and leukemia. https://healthymaterialslab.org/tool-guides/hml-resources