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Laitance—An accumulation of finer particles on the surface of fresh concrete due to an upward movement of water (as when excessive mixing water is used).
Lag screw—A coarse threaded fastener for wood applications.
Laminator—A distributor, fabricator of faced fiberglass blanket insulation products for metal buildings.
Lap—Dimension by which a felt covers an underlying felt in BUR membrane. "Edge" lap indicates the transverse cover; "End" lap indicates the cover at the end of the roll. These terms also apply to single-ply membranes.
Lapped joint—A joint made by placing one surface to be joined partly over another surface and bonding the overlapping portions
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Layer (Plywood)—A layer is a single veneer ply or two or moreplies laminated with parallel grain direction. Two or more plies laminated with grain direction parallel is a "parallel laminated layer".
Leno fabric—An open fabric in which two warp yarns wrap around each fill yarn in order to prevent the warp or fill yarns from sliding over each other.
Life-cyde cost (LCC) method—A technique of economic evaluation that sums over a given study period the costs of initial investment (less resale value), replacements, operations (including energy use), and maintenance and repair of an investment decision (expressed in present or annual value terms).
Life cycle costing—An economic analysis technique which systematically compares economic alternatives over the useful life of the asset.
Light reflectance—The percentage of light incidence that is not absorbed by the surface.
Line printer plot—A method by which computer generated moisture maps are made.
Liner panel—A panel applied as an interior finish.
Lines of electric flux—Invisible conceptual lines connecting opposite electrical charges in a dielectric medium.
Lines per frame—The number of times that the electron beam sweeps across the face of the cathode ray tube in a TV-like display.
Live load—Live load means all loads including snow, exerted on a roof except dead, wind, and lateral loads.
LN2—Liquid nitrogen—the reference temperature material used by many IR imaging systems. Boiling point - 196°C or -324°F.
- Dead Load
- Impact Load
- Roof Live Load
- Seismic Load
Loads—Anything that causes a force to be exerted on a structural member. Examples of different types are:
- Wind Load
- Crane Load
- Collateral Load
- Auxiliary Load
Loose-laid membrane—A unadhered roofing membrane anchored to the substrate only at the edges and penetrations through the roof and ballasted against wind uplift by loose aggregate or pavers.
Louver—An opening provided with a fixed or movable, slanted fins to allow flow of air.
Low carbon sheet steel—Steel containing carbon up to about 2% and only residual quantities of other elements, except those added for dioxidation, with silicon usually limited to 0.60% and manganese to about 1.65%. Also termed "plain carbon steel," "ordinary steel," and "straight carbon steel."
Low speed neutron—A high-speed neutron that has been slowed down after repeated collisions with a hydrogen atom. (See Ther-malizing)
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