Half-gabled: See Shed Roof.
Half-hipped Roof: See Gambrel Roof.
Half Principal: A principal rafter that does not go all the way to the ridgepole and is supported by a purlin at its upper end.
Half Slating: See Open Slating.
Half Span Roof: A lean-to roof. A roof that slopes in only one direction, supported by a wall that rises above the roof at the high end.
Half Truss: A jack truss shaped like half of a normal truss, with a vertical member at the high end.
Hammer Beam: Either of a pair of short horizontal members at the top of opposite walls which support a principal rafter in place of a tie beam.
Hammer-beam Roof: A decorative, timber-framed roof supported by hammer beams.
Hammer Brace: A curved brace that supports the interior end of a hammer beam.
Hand-tabbing: An installation technique for improving the performance, appearance, and wind resistance of asphalt shingles, in which roofing cement is applied in spots under the edge of the shingles.
Hatch: Roof Hatch. An opening in a roof with a weathertight, hinged cover which provides access to a roof from the interior of the building.
Header: In framing, a horizontal structural member at the top of an opening such as a door or a window.
Head Flashing: The flashing installed at the top of a window or door to direct water out and away from the opening in the wall.
Headlap: The minimum distance that the topmost course or ply of a multiple-layer roofing application, such as shingles or felts, overlaps the bottommost course or ply.
Heat Aging: A laboratory testing technique in which materials are subjected to elevated temperatures over time to accelerate age-related deterioration.
Heat and Smoke Vents: Covered openings in a roof that function as an active fire protection measure, intended to open during a fire and vent out the heat and smoke resulting from a fire within the building.
Heating Degree Day (HDD): A measurement intended to quantify the energy requirements of heating a building. HDDs are calculated using outside air temperatures by subtracting the mean daily temperature from a base temperature (above which the building should need no further heating) and summing up the positive values over an entire year. The base temperature varies by jurisdiction but is usually set at around 65°F (18°C).
Heat Seaming: See Heat Welding.
Heat Sink: (During the application of sprayed polyurethane foam), a cold substrate that absorbs the heat of the chemical reaction, slowing down the process and the foaming action of the material.
Heat Transfer: The movement of thermal energy from one physical system to another through conduction (direct contact and the exchange of kinetic energy by particles), convection (the movement of a gas or liquid), or radiation (via the photons in electromagnetic waves).
Heat Welding: The process of joining together the overlapping edges of thermoplastic membrane sheets by heating them with hot air until they fuse. Also known as "heat seaming".
Helm Roof: A steeply pitched pyramid-shaped roof with four gable ends that forms a spire.
Hem: In metalworking, the edge created by folding sheet metal back flush with itself; this is generally done for safety reasons or to improve dimensional stability.
Hex Shingles: Hexagonal shingles: Shingles whose visible areas are hexagonal after installation.
Hidden Nailing: See Blind Nailing.
Hiding Power: Covering power. Refers to coatings. The ability to hide the surface that a coating has been applied to.
Hip: The sloped edge at the intersection of two sloped roof sections.
Hip and Valley Roof: A roof that has both hips and valleys.
Hip Bevel: The angle between two sloped roof sections which are separated by a hip.
Hip Rafter: A rafter situated at the intersection of two roof sections on a hipped roof.
Hip Roof: A sloped roof with all (four) sides sloping down at the same angle, with hips where the different roof sections intersect. A hip roof has no gable ends.
Hip Shingles: Hip and ridge shingles. Shingles used to cover the edges formed by the intersection of two sloped roof sections.
Hip Tile: A specially-shaped tile used on the hip of a tiled roof.
Hoist: A device for raising or lowering people, materials, or equipment.
Holiday: An area where someone missed a spot during the application of paint or other coating material.
Honeycombing: Small voids in the surface of concrete due to the failure of the fine material in the mix to fill the spaces around the aggregate.
Horsefeathers: See feathering strip.
Hot-dip Galvanization: A galvanization process in which iron or steel is coated by being submerged in a bath of molten zinc.
Hot Stuff: Hot.
Humidity: The amount of moisture in the air, usually expressed as a percentage.
Hung Gutter: A trough suspended from the edge of the roof to collect and channel water flowing off the roof, usually to a downspout.
HVAC: An acronym for Heating, Ventilation, and Air Conditioning.
Hydration: Mineral hydration of cement. The chemical reaction in which molecular compounds in Portland cement bond with water molecules to form a new crystalline structure, strengthening the material.
Hydrodynamic: Relating to the motion and forces of fluids.
Hydrodynamic Load: Structural load resulting from moving water that is in contact with a building.
Hydrostatic: Relating to the characteristics of fluids at rest.
Hydrostatic Load: Structural load resulting from water that is not moving or is moving very slowly
Hydrostatic Pressure: The pressure exerted by a static fluid due to its weight.
Hygrometer: An instrument used to measure the humidity of the surrounding air.
Hygroscopic: Refers to a material that tends to absorb moisture from the surrounding air.
Hypalon: DuPont’s trademark name for chlorosulfonated polyethylene (CSPE), which is used as a single-ply roofing membrane material. DuPont ceased production of Hypalon in 2010, although CSPE membrane is still manufactured by others.