PARAPET WALL- A low
wall around the perimeter of a
roof deck.
PARGE COAT- A thin
application of plaster for
coating a wall.
PASS- The term used to
describe the application of one
layer of Spray Polyurethane Foam
(SPF). The speed of a pass will
determine foam thickness.
PASS LINE- The
distinct line formed between two
passes of SPF. This line is the
top skin of the bottom pass of
the SPF.
PAVER STONES- Usually
pre-cast concrete slabs used to
create a traffic surface.
PENETRATION- Any
object that pierces the surface
of the roof.
PENTHOUSE- A
relatively small structure built
above the plane of the roof.
PERLITE- An aggregate
formed by heating and expanding
siliceous volcanic glass.
Perlite in a fluffy heat
expanded form is used in
lightweight insulating concrete,
fire-resistant rigid insulation
board (R = 2.78 per inch) and
potting soil.
PERMEABILITY- The rate
of flow of a liquid or gas
through a porous material.
PHASE CONSTRUCTION- In
roofing the practice of applying
the felt plies of the built-up
roofing membrane in two or more
operations, separated by a delay
of at least one day.
PHOTO-OXIDATION-
Oxidation caused by rays of the
sun.
PIPE BOOT- A
prefabricated flashing piece
used to flash around circular
pipe penetrations. Also known as
a Roof Jack.
PITCH- A term
frequently used to designate
coal tar pitch.
PITCH PAN OR POCKET- A
bottomless metal box placed on
the roof around irregular
projections. These are
subsequently filled with coal
tar pitch or mastic to create a
weather tight seal.
PLASTICIZERS- Material
incorporated into rubber and
plastic in order to increase
their flexibility and
workability.
PLASTIC CEMENT- A term
used to describe Type I asphalt
roof cement. Plastic cement
should not be used on vertical
surfaces.
PLY- A single course
of roofing felts or reinforced
membrane.
PLYWOOD- Wooden panels
formed by gluing thin sheets of
wood together, with the grain of
adjacent layers arranged at
right angles.
POINTING- The process
where joints between masonry
units, brick, etc., are filled
with mortar.
PONDING- The
accumulation of water at
low-lying areas on a roof.
POLYMER- A substance
consisting of large molecules
which have been formed from
smaller molecules of similar
make-up.
POLYURETHANE- Any of
various polymers with a urethane
base.
PONDING- A condition
where water stands on a roof for
prolonged periods due to poor
drainage and/or deflection of
the deck.
POP RIVETS- Fasteners
used to join pieces of metal
that are installed by either
compressed air assisted or hand
operated guns. Unique in that
they are installed from one side
of the work.
POROSITY- The density
of substance and its capacity to
pass liquids.
POUR COAT- The top
coating of bitumen on a built-up
roof.
POWER VENTS-
Electrically powered fans used
to move air from attics and
structures.
PRECAST- Concrete
building components which are
formed and cured at a factory
and then transported to a work
site for erection.
PREVAILING WIND- The
most common direction of wind
for a particular region.
PRIMER- A material of
relatively thin consistency
applied to a surface for the
purpose of creating a more
secure bonding surface.
PROJECTION- Any object
or equipment which pierces the
roof membrane.
PROTECTION BOARD-
Heavy asphalt impregnated boards
which are laid over bituminous
coatings to protect against
mechanical injury.
PUNCTURE RESISTANCE-
The ability of a material to
withstand being pierced by a
sharp object.
PURLINS- A horizontal
structural member spanning
between beams or trusses to
support a roof deck.
PVC- Polyvinyl
Chloride.
R-VALUE- The measure
of a material’s resistance to
heat flow. The higher a
material’s R-value, the more it
insulates.
RAFTER- The structural
member extending from the
downslope perimeter of a roof to
the ridge or hip and is designed
to support the roof deck and
roof system components.
RAGGLE BLOCK- A
specially designed masonry block
having a slot or opening into
which the top edge of the roof
flashing is inserted and
anchored.
RAKE- The angle of
slope of a roof rafter, or the
inclined portion of a cornice.
REFLECTIVE- A term
referring to a material that has
a white or shiny metallic
surface.
REGLET- A horizontal
slot, formed or cut in a parapet
or other masonry wall, into
which the top edge of
counterflashing can be inserted
and anchored.
RE-IMPREGNATE- To
replace oils and bitumen in the
components of the solvent based
BUR which through weathering and
oxidation, have been lost.
RESIN- The "B"
component in SPF that is mixed
with the "A" component in order
to form polyurethane. Resin
contains a catalyst, fire
retardants, a blowing agent,
Polyol, and a surface active
agent.
RIDGE- The line where
two planes of roof intersect,
forming the highest point on the
roof that runs the entire length
of the roof.
RIDGE CAP- Material
applied over the ridge or hip of
a roof.
RIDGE COURSE- The
final course of roofing applied
that covers the area where two
or more roof planes intersect.
RIDGE VENT- An exhaust
venting device located at the
ridge of a roof that works in
conjunction with a starter or
under eave soffit vent and is
used to ventilate attics. Ridge
vents and their cooperative
starter or soffit vents should
be installed at a 1-1 ratio in
order to function properly.
ROOF- The assembly of
interacting components designed
to weatherproof and normally to
insulate a buildings surface,
separated from adjacent
assemblies by walls or changes
in elevation.
ROOF COATING- A
bituminous material, either a
cutback or an emulsion, to
protect the surface of the BUR
but not necessarily to
re-impregnate it.
ROOF DECK- That
component in building
construction, which forms a
platform on which the remainder
of the BUR components are
placed.
ROOF DRAIN- The
termination or fitting at the
roof of an interior drain or
leader, for draining rain water
from nominally flat roofs.
ROOF LOUVERS- Rooftop
rectangular shaped roof vents.
Also called box vents, mushroom
vents, airhawks, soldier vents.
ROOF PLANE- A roofing
area defined by having four
separate edges. One side of a
gable, hip or mansard roof.
ROOF SEAMER- A
mechanical device used to crimp
metal roof panels and make the
seams watertight, OR a machine
used to weld membrane laps of
PVC (Thermoplastic) roofing
material.
ROOF SLOPE- The angle
made by the roof surface plane
with the horizontal plane and
expressed as the amount of
vertical rise for every twelve
inch (12") horizontal run. For
instance, a roof that rises four
inches (4") for every twelve
inch (12") horizontal run, is
expressed as having a "four in
twelve" slope; often written as
"4-12." Expressed as a
percentage, the slope would be
33%, which is equal to 4 divided
by 12. Also known as the Pitch
of a roof.
ROOF SYSTEM- General
term referring to the waterproof
covering, roof insulation, vapor
barrier, if used and roof deck
as an entity.
RUN- The horizontal
distance between the eaves and
the ridge of the roof, being
half the span for a symmetrical
gable roof.
