UL (Underwriters'Laboratories) - An independent testing agency that checks electrical devices and other components for possible safety hazards.
Ultraviolet Degradation - A reduction in certain performance limits caused by exposure to ultraviolet light.
Undercoat - A coating applied prior to the finishing or top coats of a paint job; may be the first of two or the second of three coats; a.k.a. prime coat.
Underground Plumbing - The plumbing drain and waste lines that are installed beneath a basement floor.
Underlayment - 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.
Union - A plumbing fitting that joins pipes end-to-end so they can be dismantled.
Utility Easement - The area of the earth that has electric, gas, or telephone lines; may be owned by the homeowner, but the utility company has the legal right to enter the area as necessary to repair or service the lines .