01 May 1999
Incline--The slope of a roof expressed in
dielectric seaming, the heat is induced within
percent or in the number of vertical units of rise
per horizontal unit of run.
Heat transfer--The transmission of thermal
Inorganic, adj--Comprising matter other than
energy from a location of higher temperature to
hydrocarbons and their derivatives, or matter not
a location of lower temperature. This can occur
of plant or animal origin.
Insulation--See Thermal Insulation.
Hip roof--A roof which rises by inclined planes
from all four sides on the building. The line
Internal pressure--Pressure inside a building, a
where two adjacent sloping sides of a roof meet
function of wind velocity, building height, and
is called the Hip.
number and location of openings.
Homopolymer--A natural or synthetic high
lsocyanate--A highly reactive chemical grouping
polymer derived from a single monomer.
carbon atom bonded to an oxygen atom;
Holiday--An area where
=N=C=O; a chemical compound, usually
material is missing, a void.
organic, containing one or more isocyanate
Hot-dip metallic coating--Adherent protective
coating applied by immersing steel in a molten
bath of coating material.
foam insulation board.
Hood--Cover, usually light gage metal, over
Joist -- Any of the small timbers or metal beams
piping or other rooftop equipment.
arranged parallel from wall to wall to support a
floor, ceiling or roof of a building.
"Hot stuff" or "hot"--A roofer's term for hot
Kesternich test--Simulates acid rain conditions
by subjecting samples to a sulfur dioxide
Humidity--The amount of moisture contained in
atmosphere as well as condensing moisture.
the atmosphere. Generally expressed percent
relative humidity. (The ratio of the vapor
pressure to the saturation pressure for given
downspout section used to direct water away
conditions times 100.)
from a wall.
Humidity test--A test involving exposure of
Laitance -- An accumulation of finer particles on
specimens at controlled levels of humidity and
the surface of fresh concrete due to an upward
movement of water (as when excessive mixing
water is used).
Hydrocarbons--An organic chemical compound
containing mainly the elements carbon and
Lap--Dimension by which a felt covers an
hydrogen. Aliphatic hydrocarbons are straight
underlying felt in BUR membrane. "Edge" lap
indicates the transverse cover; "End" lap
Aromatic hydrocarbons are carbon-hydrogen
indicates the cover at the end of the roll. These
compounds based on the cyclic or benzene ring.
terms also apply to single-ply membranes.
They may be gaseous (CH4, ethylene,
butadiene), liquid (hexene, benzene), or solid
Lapped joint--A joint made by placing one
(Natural rubber, napthalene, cispolybutadiene).
surface to be joined partly over another surface
and bonding the overlapping portions.
retaining atmospheric moisture.
Layer (Plywood)--A layer is a single veneer ply
or two or more plies laminated with parallel grain