Glossary: L


Label Service (UL)Program allowing a manufacturer to place Underwriters Laboratories Inc. labels on his products that have met UL requirements. A UL representative visits the manufacturing location to obtain samples of the products for testing by UL. In some cases, samples are also purchased on the open market for testing. The public is thereby assured that products bearing the UL label continually meet UL specifications.
LacquerA fast-drying clear or pigmented coating that dries by solvent evaporation.
LaminateA material made by bonding several layers of material.
Laminate WoodA product made by bonding layers of wood or other material to a wood substrate.
Laminated GlassGlass panels that have outer layers of glass laminated to an inner layer of transparent plastic.
Laminated Veneer LumberA structural lumber manufactured from wood veneers so that the grain of all veneers runs parallel to the axis of the member.
LampA general term used to describe the source of artificial light. Often called a bulb or tube.
Landing Zone, ElevatorThe area 18 inches (5490 mm) above or below the landing floor.
Latent HeatHeat involved with the action of changing the state of a substance, such as changing water to steam.
Lateral ForceA force acting generally in a horizontal direction, such as wind against an exterior wall or soil pressure against a foundation wall.
Lateral LoadsLoads moving in a horizontal direction, such as the wind.
LatexA water-based coating, such as styrene, butadiene, acrylic, and polyvinyl acetate.
LathThe base material for the application of plaster.
Leaks (Sound)Small openings at electrical boxes and plumbing, cracks around doors, loose-fitting trim and closures all create leaks that allow sound to pass through, reducing the acoustical isolation of a wall, floor or ceiling system.
Ledger StripStrip fastened to the bottom edge of a flush girder to help support the floor joists.
Leveling PlateA steel plate set in grout on top of a concrete foundation to create a level bearing surface for the base of a steel column.
Life-Cycle CostingSelection of the most economical material and systems based on initial costs, maintenance costs and operating costs for the life of the building.
Lift-Slab ConstructionA method of building site-cast concrete buildings by casting all the floor and roof slabs in a stack on the ground and lifting them up the columns with a series of jacks and welding them in place.
LightA pane of glass.
Light-Gauge Steel Structural MembersLoad-bearing members formed from light-gauge steel rolled into structural shapes.
Lighting FixtureSee luminaire.
Lighting OutletAn electrical outlet to which a light fixture is connected.
Lightweight Steel FramingStructural steel framing members made from cold-rolled lightweight sheet steel.
LigninAn amorphous substance that penetrates and surrounds the cellulose strands in wood, binding them together.
LimeA white to gray powder produced by burning limestone, marble, coral, or shells.
LimestoneA sedimentary rock consisting of calcium and magnesium.
Limiting HeightMaximum height for design and construction of a partition or wall without exceeding the structural capacity or allowable deflection under given design loads.
LintelHorizontal member spanning an opening such as a window or door. Also referred to as a Header.
Liquid LimitRelated to soils, the water content expressed as a percentage of dry weight at which the soil will start to flow when tested by the shaking method.
Live LoadPart of the total load on structural members that is not a permenant part of the structure. May be variable, as in the case of loads contributed by the occupancy, and wind and snow loads.
LoadForce provided by weight, external or environmental sources such as wind, water and temperature, or other sources of energy.
Load-BearingCarrying an imposed load.
Loomed ConstructionCarpet formed by bonding the pile yarn to a rubber cushion.
Lot AreaTotal horizontal area within the lot lines of a parcel of land.
Lot LineThe boundary line of a lot.
LoudnessSubjective response to sound pressure, but not linearly related thereto. A sound with twice the pressure is not twice as loud. See Decibel.
LouverOpening with slanted fins (to keep out rain and snow) used to ventilate attics, crawl spaces and wall openings.
Low-E GlassA low-emissivity glass that has a thin metallic coating that selectively reflects ultraviolet and infrared wavelengths of the energy spectrum.
Low-Emissivity CoatingA surface coating used on glass that permits the passage of most shortwave electromagnetic radiation (light and heat) but reflects longer-wave radiation (heat).
Low-Slope RoofsRoofs that are nearly flat.
LumberA product produced by harvesting, sawing, drying, and processing wood.
Lumber GraderA person who inspects each piece of lumber and assigns a grade to it.
Lumber, BoardsLumber nominally less than 2 inches thick and 2 inches or more in width.
Lumber, DimensionLumber cut and dressed to standard sizes.
Lumber, Dressed SizeThe size of lumber after it has been cut to size and the surfaces planed.
Lumber, Machine Stress-RatedLumber that has been mechanically tested to determine its stiffness and bending strength.
Lumber, MatchedLumber that is edge dressed to make close tongue-and-groove edge joints.
Lumber, Nominal SizeThe size of lumber after it has been sawn to size but has not been surfaced.
Lumber, PatternedLumber that is shaped to a pattern or to a molded form.
Lumber, RoughLumber that has not been surfaced but may be sawn, edged, and trimmed.
Lumber, ShiplappedLumber that is edge dressed to make a lapped joint.
Lumber, Shop and FactoryLumber intended to be cut up and used in some manufacturing process.
Lumber, StructuralLumber that is intended for use where allowable strength or stiffness of the piece is known.
LumenA unit for measuring the flow of light energy.
LuminaireA complete lighting unit consisting of one or more lamps plus elements needed to distribute light, hold and protect the lamps, and connect power to the lamps. Also called a lighting fixture.
Luminancethe luminous intensity of a surface of a given area viewed from a given direction.
Luminance MeterA photoelectric instrument used to measure luminance. Also called a light meter.
LuminescenceThe emission of light not directly caused by incandescence.
Luminous FluxThe rate of flow of light energy through a surface, expressed in lumens.
Luminous IntensityThe force that generates visible light express by candela, lumens per steradian, or candlepower.
Luminous TransmittanceA measure of the capacity of a material to transmit incident light in relation to the total incident light striking it.
LuxA unit of illumination equal to 1 lumen per square meter.