VALLEY- A term applied
to a depressed angle formed by
the meeting of two inclined
slopes of a roof.
VAPOR- The gaseous
form of any substance.
VAPOR MIGRATION- The
natural movement of water vapor
from regions of higher vapor
pressure to regions of lower
vapor pressure.
VAPOR PRESSURE- The
pressure at which a liquid and
its vapor are in equilibrium at
a definite temperature.
VAPOR RETARDER- A
material used to restrict the
passage of water vapor through a
roof assembly.
VEINING- The
characteristic lines or "stretch
marks" which develop during the
aging process of soft bitumens.
Veneer- Any of the thin layers
of wood glued together to make
plywood.
VENT- An opening or
device used to permit air or
vapors to exit an enclosed
structure.
VENT PIPE- A vertical
pipe of relatively small
dimensions which protrudes
through a roof to provide for
the ventilation of gasses.
VENTILATION SHORT CIRCUIT-
The disruption of air flow in an
intake-exhaust ventilation
system. For instance, if vents
such as turbine vents or gable
vents are placed in between the
intake vents and exhaust vents
(such as soffit and ridge vents)
then the draw created by the
stack effect will be disrupted
and the ventilation system will
be much less effective.
VENTILATOR- Device
installed on the roof for the
purpose of ventilating the
interior of the building.
VENTING- The process
of installing roof vents in a
roof assembly to relieve vapor
pressure, OR the process of
water in the insulation course
of the roof assembly evaporating
and exiting via the roof vents.
VERMICULITE- An
aggregate somewhat similar to
perlite that is used as an
aggregate in lightweight roof
decks and deck fills. It is
formed from mica, a hydrous
silicate.
VERTICAL APPLICATION-
Roll roofing laid parallel to
the slope of a roof.
VISCOSITY- The
internal frictional resistance
offered by a fluid to change of
shape or to the relative motion
or flow of its parts.
VULCANIZE- To improve
the strength, resiliency, and
freedom from stickiness and odor
of rubber, for example, by
combining with sulfur or other
additives in the presence of
heat and pressure.
WALKWAYS- Designated
areas for foot traffic on roofs.
WATER ABSORPTION- The
increase in weight of a test
specimen expressed as a
percentage of its dry weight
after being immersed in water
for a specified time at a given
temperature.
WATER GUARD- A turned
up edge on valley metal or
continuous wall flashing; used
to prevent water migration under
the roof system.
WARM WALL- The
finished wall inside of a
structure, used in roofing to
determine how to install
waterproof underlayments at
eaves.
WARRANTY- The written
promise to the owner of roofing
materials for material related
problems.
WATER STOP- A device
designed to protect the exposed
edge of a partially installed
BURM from water entrance.
WATERPROOFING- The
process where a building
component is made totally
resistant to the passage of
water and/or water vapor.
WATER VAPOR- Moisture
existing as a gas in air.
WEEP HOLE- A hole that
allows for drainage of entrapped
water from masonry structures.
WELD- The joining of
components together by fusing.
In thermoplastics, refers to
bonding together of the membrane
using heat or solvents.
WIND UPLIFT- The
upward force exerted by wind
traveling across a roof.
WRINKLE- A raised
pattern of ridges running in a
random fashion in a BUR.
Z
ZINC- A bluish-white,
lustrous metallic element that
is brittle at room temperature
but malleable with heating. It
is used to form a wide variety
of alloys including brass,
bronze, various solders, and
nickel silver, in galvanizing
iron and other metals, for
electric fuses, anodes, and
meter cases, and in roofing,
gutters, flashings, edge metals
and also for various household
objects. Atomic number 30;
atomic weight 65.37; melting
point 419.4 °C; boiling point
907 °C; specific gravity 7.133
(25 °C); valence 2.
ZONOLITE- A
lightweight, insulating concrete
composed of portland cement,
water, and vermiculite
aggregate.
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