Roofing Terms

aggregate

Crushed stone, crushed slag or water-worn gravel
used for surfacing a built-up roof membrane.

alligatoring

The cracking of the surface bitumen on a built-up roof,
producing a pattern of cracks similar to an alligator's hide; the cracks
may not extend through the surfacing bitumen.

asphalt

A dark brown to black cementitious material in which the
predominating constituents are bitumens which occur in nature or are obtained
in petroleum processing.

base sheet

A saturated or coated felt placed as the first ply in
a multiple-ply built-up roofing membrane.

base flashing

See flashing

bitumen

1. A class of amorphous, black or dark colored, (solid,
   semi-solid or viscous) cementious substances, natural or manufactured,
   composed principally of high molecular weight hydrocarbons, soluble in carbon
   disulfide, and found in asphalts, tars, pitches and asphaltites.
2. A generic term used to denote any material composed principally of bitumen.
3. In the roofing industry there are two basic
   bitumens: asphalt and coal-tar pitch.
   Before application they are either:
   1. heated
   2. dissolved in a solvent
   3. emulsified

bituminous, adj.

Containing or treated with bitumen. Examples are
bituminous concrete, bituminous felts and fabrics,
bituminous pavement.

blister

An enclosed pocket of air mixed with water vapor, trapped
between impermeable layers of felt.

bond

Adhesive and cohesive forces holding two roofing components
in intimate contact.

built-up roofing

A continuous, semi-flexible membrane consisting of
plies of saturated felts, coated felts, fabrics or mats assembled in place
with alternate layers of bitumen and surfaced with mineral aggregate, bituminous
material or a granule surfaced sheet, commonly abbreviated BUR.

cant strip

A beveled strip used under flashing to modify the angle
at the point where the roofing or waterproofing membrane meets any vertical
angle.

cap flashing

See flashing

cap sheet

A granule-surfaced coated felt used as the top ply of a
built-up roof.

caulking

A composition of vehicle and pigment, used at ambient
temperatures for filling joints, that remains plastic for an extended time
after application.

coal tar

A dark brown to black cementitious material produced by
the destructive distillation of coal.

coping

A covering on top of a wall, such as a parapet, exposed to
the weather, usually sloped to carry off water.

cornice

1. A horizontal molded projection that crowns or completes
   a building or wall.
2. The uppermost part of an entablature.

counter flashing

Formed metal or elastomeric sheeting secured on or
into a wall, curb, pipe, roof-top unit or other surface to cover and protect
the upper edge of a base flashing and its associated fasteners.

deck

The structural surface to which the roofing or waterproofing
system is applied.

drip edge

An L-shaped strip of metal placed at the edge of a roof's
eaves underneath roofing felt and on top of the roofing felt at the edges
a roof's rakes.

eaves

The projecting overhang at the lower edge of a roof.

edge stripping

Application of felt strips cut to narrower widths
than normal felt roll width to cover a joint between flashing and built-up
roofing.

edging

Flashing that forms or serves as an edge or border to the
roofing membrane.

efflorescence

A deposit or encrustation of soluble salts, generally
white and most commonly consisting of calcium sulfate, that may form on the
surface of stone, brick, concrete or mortar when moisture moves through and
evaporates on the masonry. Often caused by free alkalis leached from mortar,
grout or adjacent concrete.

expansion joint

A structural separation between two building elements
without damage to the roofing or waterproofing system.

fascia

A flat horizontal band between moldings.

felt

A flexible sheet manufactured by the interlocking of fibers
through a combination of mechanical work, moisture and heat without spinning,
weaving or knitting. Roofing felts are manufactured from vegetable fibers
(organic felts), asbestos fibers (asbestos felts) or glass fibers (glass felts)

fishmouth

1. A half cylindrical or half conical opening formed by
   an edge wrinkle or failure to embed a roofing felt.
2. In shingles, a half-conical opening formed at an edge.

flashing

The system used to seal membrane edges at walls, expansion
joints, drains, gravel stops and other places where the membrane is interrupted
or terminated. Base flashing covers the edges of the membrane. Cap or
counterflashing shields the upper edges of the base flashing.

gravel stop

A flanged device, frequently metallic, designed to prevent
loose aggregate from washing off the roof and to provide a continuous finished
edge for the roofing.

hip

The external angle formed by the meeting of two adjacent sloping
sides of a roof.

hot

A roofer's term for hot bitumen.

incline

The slope of a roof expressed in percent or in the number
of vertical units of rise per horizontal unit of run.

lap

verb
To place or lay a layer of felt so as to cover part of
another; overlap.

noun

1. The amount by which a felt overlaps another.
2. A continuous ply of felt laid on a roof.

membrane

A flexible or semiflexible roof covering or waterproofing
whose primary function is the exclusion of water.

mud cracking

A surface cracking resembling a dried mud flat.

overhang

The projecting part of a roof that extends beyond a wall.

parapet

That part of any wall rising entirely above the roof.

penetration

Any object such as a pipe that goes through the roof membrane.

pitch pan

A flanged, open bottomed metal container placed around
a column or other roof penetration and filled with hot bitumen or flashing
cement to seal the joint.

pitch pocket

See pitch pan

ply

A layer of felt in a built-up roofing membrane; a four-ply membrane
has at least four plies of felt at any vertical cross section cut through
the membrane.

pond

A surface which is incompletely drained.

rake

The sloped edge of a roof at the first or last rafter.

reglet

A groove in a wall or other surface adjoining a roof surface
for the attachment of counterflashing.

ridge

The horizontal line formed by the juncture of two sloping surfaces of a roof.

ridging

An upward, tenting displacement of a roofing membrane, frequently
over an insulation joint.

shark fin

An upward curled sidelap or endlap.

shingle

1. A small unit of prepared roofing material designed for
   installation with similar units on overlapping rows on inclines normally
   exceeding 25 percent.
2. To cover with shingles.
3. To apply any sheet material in overlapping rows like shingles.

slippage

Relative lateral movement of adjacent components of a built-up
membrane. It occurs mainly in roofing membranes on a slope, sometimes exposing
the lower plies or even the base sheet to weather.

slope

The tangent of the angle between the roof surface and the
horizontal plane, expressed as a percentage, or in inches of rise per foot
of horizontal distance. See also incline.

spall

noun
A chip, fragment or flake from a piece of masonry such
as stone, brick, ceramic tile or concrete.

verb
To break up into chips or fragments.

split

A membrane tear resulting from tensile stress.

stack vent

A vertical outlet in a built-up roofing system to relieve
the pressure exerted by water vapor between the roofing membrane and the
deck.

stripping

1. The technique of sealing a joint between metal and built-up
   membrane with one or two plies of felt or fabric and hot or cold applied
   bitumen.
2. The technique of taping joints between insulation boards or deck
   panels. Also called strip flashing.

substrate

The surface upon which the roofing or waterproofing membrane
is placed, i.e. structural deck or insulation.

tapered edge strip

A tapered insulation strip used to elevate the
roofing at the perimeter and at penetrations of the roof.

tar

A brown or black bituminous material, liquid or semisolid in
consistency, in which the elements are obtained as condensates in the processing
of coal, petroleum, oil-shale, wood or other organic materials.

through wall flashing

A water resistant membrane or material
assembly extending totally through a wall and its cavities, positioned to
direct any water within the wall to the exterior.

vent

An opening designed to convey water vapor or other gas from
inside a building or a structure to the atmosphere.