====== Roofing Glossary: I to L ======



===== I =====


==== Ice Dam ====
  * a mass of ice formed at the transition from a warm to a cold roof surface, frequently formed by refreezing melt water at the overhang of a steep roof, causing ice and water to back up under roofing materials.


==== Incline ====
  * The slope of a roof expressed in percent or in the number of vertical units of rise per horizontal unit of run.


==== Insulation ====
  * a material applied to reduce the flow of heat.



===== 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.


===== K =====



===== L =====

==== 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.


==== 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.