|
Note: It is very important
to understand the terminology of any subject you wish to have
a working knowledge of. We have listed specialty words and
their definitions below and we have included drawings to illustrate
many of the terms.
Base flashing: That portion
of the flashing attached to or resting on the deck to direct
the flow of water onto the roof covering.
| Batten: Also
referred to as Purlins, see Purlin or Purloin. Batten
or Purlins can be 1"x2"x4' wood strips nailed
to the roof or rafters, upon which the roofing is attached.
In some instances they are also steel lengths measuring
about an inch or so wide that have an elevated middle
where one screws the metal roofing into. Sometimes called
“hat channel” because of its shape. Battens
or purlins are attached to roof decking to give a secure
base to anchor the roofing materials to because many OSB
(chip board sheets appearing much like plywood) will not
hold a screws properly. |
|
Bird stop: In addition
to preventing birds from nesting in the hollows of the clay
tile style of metal roofing , this length of formed metal
or foam elevates the first course of tile so that it is positioned
at the same angle as subsequent courses.
Caulk: To fill a joint
with mastic or asphalt cement to prevent leaks.
Chalk line: A line made on the roof by snapping a taut string
or cord dusted with chalk. Used for alignment purposes.
Class "A":
The highest fire-resistance rating for roofing. Indicates
roofing is able to withstand severe exposure to fire originating
from sources outside the building.
Class "B":
Fire-resistance rating that indicates roofing materials are
able to withstand moderate exposure to fire originating from
sources outside the building.
Class "C":
Fire-resistance rating that indicates roofing materials are
able to withstand light exposure to fire originating from
sources outside the building.
Collar: Pre-formed flange
placed over a vent pipe to seal the roof around the vent pipe
opening. Also called a vent sleeve.
Counter flashing: That
portion of the flashing attached to a vertical surface to
prevent water from migrating behind the base flashing.
Cricket: A peaked saddle
construction at the back of a chimney to prevent accumulation
of snow and ice and to deflect water around the chimney.
Deck: Also known as Decking.
The surface installed over the supporting framing members
of a building. It is the structural "skin" of a
roof over which roofing in applied. Most new homes have decking
made of plywood. There are four main types of decking commonly
used on residential roofing projects:
- Plywood: Plywood is
strong, durable, and light. It comes in many grades with
ratings from A to D. Use only exterior grade plywood for
decking. The thickness of plywood depends on the spacing
of the rafters.
- OSB:
Oriented strand board (OSB) is cheaper than plywood, but
not as strong as plywood, and does not hold nails as well
as plywood. One side has a slip resistant coating and should
be placed facing up.
- Tongue and groove 2-by-6:
If a roof will be seen from the inside (no ceiling installed),
tongue and groove is used. It is a wood decking that provides
great insulation without additional rigid roof insulation
in moderate climates. Also, the boards can be painted or
stained on the inside to match the interior.
- Step sheathing: Step
sheathing is used alone or in combinations with solid sheathing
for installation of tiles or shakes. Step sheathing allows
air circulations under the tiles by using 1-by-6 or 2-by-6
boards that are evenly spaced so that air can move under
the tiles or shakes.
Dormer: A framed window
unit projecting through the sloping plane of a roof.
Downspout: A pipe for
draining water from roof gutters. Also called a leader.
Drip edge: A non-corrosive,
non-staining material used along the eaves and rakes to allow
water run-off to drip clear of underlying construction.
Trim that goes here is called “drip
trim”.
Eaves: The horizontal,
lower edge of a sloped roof.
Trim that goes on these areas is referred to as “eave
trim” or sometimes “eave flashing”. (We
use the term “eave trim”.
Feathering strips: Tapered
wood filler strips placed along the butts of old roofing to
create a level surface when re-roofing over existing roofs.
Very useful when re-roofing over old shake shingles. Feathering
strips are also called horse feathers. Feathering strips are
used to level an old roof much like shims are used around
a door so that there is a level surface to attach the purlins
to.
Felt: A flexible sheet
that is saturated with asphalt and used as an underlayment,
sometimes called "tar paper"
Flashing: Pieces of special
trim used to prevent seepage of water into a building around
any intersection or projection in a roof such as vent pipes,
chimneys, adjoining walls, dormers and valleys.
- Plumbing vent flashing: Plumbing vent
flashing prevents rainwater from running into holes cut
for pipes in the roof. This flashing is sold according to
the size of the vent pipe and the roof angle. Roofing material
is installed over the flashing.
- Step flashing: Flashing application
method used where a vertical surface meets a sloping roof
plane.
- Valley flashing: This flashing is used
in open valleys of the roof. Most often leaks are found
in the valley flashings due to flashing that is nailed to
tightly to the decking or shingles that are not trimmed
far enough off the flashing.
Flashing cement: In the
application of metal roofing, flashing cement is usually a
clear silicone caulk (purchase the best grade available).
This is used to further seal any potential leaks, usually
at areas wherein flashing was applied. A small bead of flashing
cement where the flashing comes in contact with a vertical
wall is a good idea.
Gable: The upper portion
of a sidewall that comes to a triangular point at the ridge
of a sloping roof.
Trim that goes on this part of a roof is called “gable
or rake trim”. We use the term “gable trim”.
Gable roof: A type of
roof containing sloping planes of the same pitch on each side
of the ridge. Contains a gable at each end. Also see this
link: Types of Roofs.
Gambrel roof: A type
of roof containing two sloping planes of different pitch on
each side of the ridge. The lower plane has a steeper slope
than the upper. Contains a gable at each end. Also see this
link: Types of Roofs.
Gutter: The trough that
channels water from the eaves to the downspouts.
Hip: The inclined external angle formed by the intersection
of two sloping roof planes. Runs from the ridge to the eaves.
Hip roof: A type of roof
containing sloping planes of the same pitch on each of four
sides. This type of roof does not contain a gable(s). Also
see this link: Types of Roofs.
Ice dam: Ice dams occur
when snow melts near the ridgelines of warm roofs (roofs without
adequate ventilation). As the water runs down the roof to
the overhang, it cools and freezes. If the snow continues
this melt and freeze process, an ice dam can form that can
seep under the shingles, through the decking and into the
house. This, of course, can cause serious roof leaks--even
in freezing temperatures.
The best prevention to ice dams is a well-ventilated
(cool) roof. Additional protection for your roof can be applied
with an impermeable ice and water membrane. The membrane is
installed on top of the decking, under the roofing material.
Temporary prevention of ice dams can also be done through
the use of electric cables along the eaves of the roof (where
the dams usually form). However, new ice dams can form above
the cables and still cause extensive damage. Another emergency
solution to ice dams is to fill a sock or nylon with calcium
chloride. Lay the stocking vertically across the ice dam.
The calcium chloride will melt the ice and release the water
so that it can drain outside, and not inside your roof.
Intake Ventilation: The
part of a ventilation system used to draw fresh air in. Usually
vents installed in the soffit or along the eaves of a building.
Lean-to roof: A roof
with one slope only that is built against a higher wall.
Low slope application:
Method of installing roofing material on roof slopes between
one and two inches per foot.
Mansard roof: A type
of roof containing two sloping planes of different pitch on
each of four sides. The lower plane has a much steeper pitch
than the upper, often approaching vertical. This type of roof
contains no gables. Also see this link: Types
of Roofs.
Metal drip edge: This
refers to trim, usually gable and eave trim, that has a slight
bend at the edge which facilitates water runoff, away from
the building. All our eave and gable trims contain this feature.
Open valley: Method of
roofing in which the roofing material on both sides of the
valley is trimmed along a chalk line snapped on each side
of the valley, leaving the valley flashing exposed. Metal
roofing always has this feature unlike certain types of shingle
roofing wherein the shingles extend into the valley, thereby
creating its own “valley flashing”.
Overhang: That portion
of the roof structure that extends beyond the exterior walls
of a building.
Pitch: Also known as
"slope", pitch is the measure of how "steep"
a roof is. For example, if a roof is a 4/12 pitch, the roof
rises 4 inches for every horizontal run of 12 inches. The
pitch of the roof is a big factor in determining the kinds
of materials that can be used and the longevity of the roof.
Usually, a steeper roof (higher pitch) will last longer due
to its better drainage capabilities.
Ply: The number of layers
of roofing: i.e. one-ply, two-ply.
Purlin:
Horizontal lengths of material (wood or metal) that are
affixed to the roof and to which the finished roofing material
is affixed.
Purlins can be wood strips
(1” x 2”) or can metal and are usually a 1”
subgirt material preferably galvanized steel. Because the
purlins elevate the new roof slightly they also contribute
to your new roofing having airflow which can help dispurse
temperatures in the heat of the day.
It’s sometimes necessary
to use purlins over an old roof as the purlins give one
the ability to do some “leveling” by using feathering
strips or shims between the purlins and the irregularities
of the old roof surface.
Here is an illustration
of a Purlin Plan showing placement of the purlins on the
roof:
Rafter: The
supporting framing member immediately beneath the deck,
sloping from the ridge to the eave.
Rake:
The inclined edge of a sloped roof over a wall from the
eave to the ridge. These two slopes meet at the peak or
ridge. Trim that goes on these slopes is referred to as
“gable or rake trim”. We typically use the term
“gable trim”.
Re-cover (overlay):
The installation of a new roof system over an existing system
without removing an existing system.
Re-roofing:
Installing a new roof system on a building that is not new.
Ridge:
The uppermost, horizontal external angle formed by the intersection
of two sloping roof planes.
Trim that covers this area is called “ridge cap”.
Rise: The
vertical distance from the eaves line to the ridge.
Run: The
horizontal distance from the eaves to a point directly under
the ridge. One half the span.
Sheathing: See
Batten. Exterior grade boards used as a roof deck material.
"Step sheathing" is used alone or in combinations
with solid sheathing for installation of tiles or shakes.
Step sheathing allows air circulations under the tiles by
using 1-by-6 or 2-by-6 boards that are evenly spaced so
that air can move under the tiles or shakes.
Shed roof:
A roof containing only one sloping plane. Has no hips, ridges,
valleys or gables.
Also see this link: Types of Roofs
Slope:
The degree of roof incline expressed as the ratio of the
rise, in inches, to the run, in feet. Also referred to as
“pitch”.
Slope Applications:
Divided into three categories, this is the application of
roofing materials to a roof based upon its slope or pitch.
The three categories are known as “steep slope application,
“normal slope application” or “low slope
application”.
-
Steep slope
application: Method of installing roofing material
on roof slopes greater than 21 inches per foot.
-
Normal slope
application: Method of installing roofing materials
on roof slopes between 4 inches and 21 inches per foot.
-
Low slope application:
Method of installing roofing materials on roof slopes
between two and four inches per foot.
Soffit:
The finished underside of the eaves.
Span:
The horizontal distance from eaves to eaves.
Square:
A unit of roof measure covering 100 square feet.
Tar paper: See
"Felt"
Tear off:
Removing an existing roof system.
Telegraphing:
A distortion that may arise when a new roof is applied over
an uneven surface.
Underlayment:
A layer of asphalt saturated (sometimes referred to as tar
paper) which is laid down on a bare deck before roofing
material is installed to provide additional protection for
the deck.
There are some great new
“rubber membrane” underlayments that are vastly
superior to the old felt paper ones. It’s a smart
idea to use these in valleys and about 36” around
the edges of your roof if not the whole roof. These new
high tech underlayments are made out of material that seals
itself around screws or nails that are driven through it.
Valley:
The internal angle formed by the intersection of two sloping
roof planes to provide water runoff. Trim that goes on this
area is called “valley trim”.
Vent:
Any outlet for air that protrudes through the roof deck
such as a pipe or stack. Any device installed on the roof,
gable or soffit for the purpose of ventilating the underside
of the roof deck.
Vent sleeve:
See collar.
|
