Headlap: the distance of overlap measured from the uppermost ply or course to the point that it laps over the undermost ply or course.

 

Heat Seaming: the process of joining thermoplastic films, membranes, or sheets by heating and then applying pressure to bring both materials in contact with each other. (See Heat Welding.)

 

Heat Welding: method of melting and fusing together the overlapping edges of separate sheets or sections of polymer modified bitumen, thermoplastics or some uncured thermoset roofing membranes by the application of heat (in the form of hot air or open flame) and pressure. (See Heat Seaming.)

 

Hem: the edge created by folding metal back on itself.

 

Hip: the inclined external angle formed by the intersection of two sloping roof planes.

 

Hip Roof: a roof that rises by inclined planes to form one or more hips.

 

Hot: the roofer’s term for hot bitumen.

 

HVAC: heating, ventilating, and air conditioning equipment.

 

HypalonTM: a registered trademark of E.I. duPont de Nemours, Inc., for “chlorosulfonated polyethylene” (CSPE). (See Chlorosulfonated Polyethylene.)

 

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