A weak layer of cement and aggregate fines on a concrete surface that is usually caused by an overwet mixture, overworking the mixture, improper or excessive finishing or combination thereof.
L
Laminate
To join layers of materials together using fusion; the process of joining layers of materials together using adhesion.
Lap
That part of a roofing, waterproofing, or flashing component that overlaps or covers any portion of the same or another type of adjacent component.
Lap Cement
An asphalt-based roof cement formulated to adhere overlapping plies or asphalt roll roofing.
Lap Seam
Occurs where overlapping materials are seamed, sealed or otherwise bonded.
Latex
A stable dispersion of polymeric substance in an essentially aqueous medium.
Lead
A soft malleable, heavy metal; has low melting point and a high coefficient of thermal expansion.
Lift
The sprayed polyurethane foam that results from a pass. It usually is associated with a certain pass thickness and has a bottom layer, center mass and top skin in its makeup.
Liquid-Applied
Application of bituminous cements, adhesives or coatings installed at ambient or slightly elevated temperatures.
Liquid-Applied Built-Up Roof
A continuous, semi-flexible roof membrane, consisting of multiple plies of felts, mats or fabrics laminated together with alternate layers of roof cements and surfaced with a liquid -applied coating with or without aggregate surfacing.
Live Loads
Temporary loads that the roof structure must be designed to support, as required by governing building codes. Live loads are generally moving and/or dynamic or environmental, (e.g., people, installation equipment, snow, ice or rain, etc.).
Loose-Laid Membrane
A ballasted roofing membrane that is attached to the substrate only at the edges and penetrations through the roof.
Low Temperature Flexibility
The ability of a membrane or other material to resist cracking when flexed after it has been cooled to a low temperature.
Low-Slope Roof
A category of roofs that generally include weatherproof membrane types of roof systems installed on slopes at or less than 3:12 (14 degrees).