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L
Laitance: An
accumulation of fine, powdery aggregate particles on fresh cement caused by the upward
movement of water; indicates that too much water was used in the mix resulting in poor
surface adhesion for a waterproofing layer.
Laminated
Shingles: See Dimensional Shingles or Architectural Shingles.
Lap: The
part of the roofing material that overlaps a section of adjacent material.
Lap Cement: Asphalt-based
roof cement used to adhere overlapping plies of asphalt roll roofing.
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Lap Seam: Where
two material that overlap are sealed together.
Lead: Metal
used for flashing material.
Leader Head: A
component used to direct water from a through-wall scupper to a downspout. Also known as a
Collector Head.
Leader Pipe: A
conduit for carrying water from a gutter, scupper, drop outlet or other drainage unit from
roof to ground level. Also known as Downspout.
Lift: The
rise in Sprayed Polyurethane Foam resulting from a pass.
Live Loads: Temporary
items on a roof such as equipment, people, snow, etc. which the roof must be designed to
support.
Loose-Laid
Roof Membranes: Roofing material attached only at the perimeter and at penetrations
and held in place by ballast, pavers, or other materials.
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