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Whitco Roofing Atlanta Georgia

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Roofing Terms J-L

Roofing Terms J – L

-J-
 
Joist
any of the small timbers, metal or wood beams arranged parallel to each other and spanning from wall to wall to support a floor, ceiling, or roof of a building.
Joule
a unit of energy or work; equals the work done by a force of 1 newton which acts over a distance of 1 meter in the direction of the force.
 
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-K-
 
k or k-Value
thermal conductivity; the time rate of heat flow through a unit area of a homogeneous material in a direction perpendicular to isothermal planes induced by a unit temperature gradient. In English (inch-pound) units of measurement, it is the number of BTUS that pass through a 1 inch (25 mm) thickness of a 1 square foot (0.09 m2) sample of material in 1 hour with a temperature difference between the two surfaces of 1° F. It is expressed as Btu•inch/h•ft2•°F.
Kerf
(1) a slit or notch made by a saw or cutting torch; (2) the width of cut made by a saw or cutting torch.
Kesternich test
simulates acid rain conditions by subjecting test specimens to a sulfur dioxide atmosphere as well as condensing moisture for the purpose of evaluating rust/corrosion characteristics.
Knee cap
a metal cover trim that fits over a panel rib after it has been cut and bent.
Knee joints
see Knuckle.
Knuckle
a metal closure, either shop-or pre-fabricated, installed over the cut seam of a continuous metal roof panel at the transition from a steep-slope roof to a vertical roof or wall.
 
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-L-
 
Laitance
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.
Laminate
to join layers of materials together using fusion; the process of joining layers of materials together using adhesion.
Laminated shingles
see Dimensional Shingles or Architectural Shingles.
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. The NRCA Roofing and Waterproofing Manual—Fifth Edition 990 Glossary
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.
Leader head
see Conductor Head.
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-slope roofs
a category of roofs that generally include weatherproof membrane types of roof systems installed on slopes at or less than 3:12 (14 degrees).
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.
 
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Glossary of Roofing Terms

  • A - C
  • D - F
  • G - I
  • J - L
  • M - O
  • P - R
  • S - U
  • V - Z
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