Roofing Terminology
When
deciding on a contractor to do work on your home it is always helpful to
be able to understand their unique language. The in depth analysis of terms that
follows provides some of the common terms associated with roofing that
you may encounter when reviewing companies and products.
A general glossary of definitions is also available by clicking here. "Glossary"
ROOFING TERMINOLOGY
Ventilation-
Proper attic ventilation can
lower the cost of cooling your home by as much as 65%, prolong the life
of roofing materials, and prevent the premature deterioration of
attic-insulation materials. In summer weather attic air can easily
super-heat to 140 degrees. The trapped air will rise to fill the attic
space and radiate heat downward along the ceiling, walls, and joists.
This seriously adds to the burden of your air conditioner, requiring it
to work almost constantly during summer weather. Super heated air will
actually scorch rafters and plywood, wilt insulation, and cause shingles
to cup and buckle. NOTE: Proper ventilation will add as much
as 10 years to the life of your roofing.
Power attic ventilators (attic fans)- Attic
fans are attached to the roof surface and are used to help clear an
attic space of super heated air. These fans have a thermostat that is
set to switch on at 100 degrees and are set to switch off at 85
degrees.
Roofline louvered vents (can style vents)-
These small square vents are on approximately 95% of houses that have
reached re-roofing stage. They are installed near the roof peak to allow
hot air to escape as it rises.
Ridge vent- This ventilation option is
installed on as much as 85% of new construction and is the only way to
properly ventilate a vaulted or cathedral ceiling. Ridge vent is
installed along the entire ridge to provide the most evenly ventilated
roof possible. It tends to be much more pleasing to the eye than
traditional vents because all that is seen is about 3/4 of an inch under
ridge cap shingles and the traditional vents are removed and roofed over
when ridge vent is installed.
Square- A square is the most common term
used to determine the actual surface measurement of a roof. A square
is an area of 10’x 10’ or 100 square feet = 1 Square.
Ice dams- Ice dam formation occurs when snow and ice
melts on the middle and upper portions of the roof and as the
melt water travels towards edges of the roof it freezes because there is
less or no heat radiating through the roof. This build-up of ice and
snow is called an ice dam and will actually, through the repeated
heating and cooling process, lift the shingles causing water to leak
into the house. As you can see from this much of the problem of ice dams
can be solved with proper ventilation, but the rest of the problem can
be solved with a second layer of protection called ice and water
shield.
Ice and water shield- Ice shield is a self
adhesive rubberized asphalt membrane that is applied to the lowest 3
feet of the roof edges. The ice shield seals around nails and will
divert any water that penetrates roofing material to run to the gutter
and not into the house or the eves. Ice and water shield is also
commonly applied to the roof deck (plywood) along the entire length of
valleys as a second layer of protection should a leak occur before the
roof comes to age for new roofing.
Drip edge- Metal drip edge runs from the gutter line to the peak on
the gable ends of the roof. The purpose of drip edge is to, primarily,
divert water coming off the roof away from the fascia. Additional
advantages are a few extra inches of protection against wind driven rain
and potential pests such as carpenter ants and bees.
Re-work chimney flashing- To make necessary
repairs on metal flashing around chimney and re-caulk and/or replace
metal if required.
Step flashing and counter flashing- Step
flashing is installed where a portion of pitched roof meets a vertical
wall. Counter flashing is installed onto wall over step flashing. NOTE:
Counter flashing is not required, in most cases, when siding is present
on wall.
Roof pitch- The steepness/rate of incline on
a roof is determined by calculating the rate of rise vs. rate of run.
Examples:
4/12 = 4 inches of rise for every 12 inches of
run (Approximately a 17 degree pitch)
12/12= 12 inches of rise for every 12 inches of run
(Exactly a 45 degree pitch)
Aging factors of roofing materials- Roofing
material deterioration can vary greatly depending on the pitch. If a
multi-pitched house has a section of 3/12 that needs to be replaced due
to excessive aging, chances are that the 10/12 section has many years of
protection left. This is true, even though both sections had the same
25-year warranty shingle. The lower the pitch, the faster the rate of
deterioration. You may find that your standard 25-year shingle lasts
only 15 years on a 2/12 pitch and the same shingle lasts 35 years on a
12/12 pitch. The other major factor in uneven aging is southern and
western exposure sides of the roof, they will nearly break down more
quickly.
Felt paper- The standard underlayment used
in shingle roofing is asphalt saturated felt paper. Available in 15lb,
30lb, or 45lb ratings(the lb. rating defines the number of pounds pre
square) the most common weight used is 15lb and is applied in about 80%
of shingle roofing, 30lb. will give you a small amount of added leak
protection and 45lb. is used mainly in wood shake/shingle roofing.
Although the felt paper does provide temporary waterproofing while the
roof is in the transition stage between tear-off and re-application of
shingles its primary function is to act as a vapor barrier
between the wood roof deck and the shingles. Without the felt layer, the
wood planking or plywood --dried by superheated temperatures found in
most attics-- will draw moisture (including tar and oils from the
asphalt) from shingles. The result will be shingles that are prematurely
worn, cracked, brittle, as well as stuck to the wood surface when
removal is attempted.
3-Tab shingles vs. Architectural shingles-
Chances are that your home currently has 3-tab shingles. As the name
describes the shingle configuration leaves 12” wide tabs exposed with
1/4” slot lines or rain groves. Though definitely functional, the 3-tab
shingle has lost much of its popularity due to the introduction of the
architectural or dementional shingle. These shingles have actually been
in existence long enough for roofers to see them come to maturity and
need replacement, but their popularity has really come to light in the
last 10 years. The architectural shingle is modeled after the look of
cedar shake shingles without the fire hazard, insect problems, rotting,
and expense. 95% of realtors will highly suggest architectural shingles
over 3-tab shingles on the basis of curb appeal and re-sale of your
home. Other advantages of architectural shingles are; heavier weight and
thicker (reducing blow-offs), less potential for curling, and they have
a textured uneven look for a clean appearance when applied over badly
deteriorated roofing.
Asphalt (organic) vs. Asphalt/Fiberglass
blend shingles- The choice of the composition of the shingles
applied to your home are basically broken down into to two categories;
Asphalt (organic) or Asphalt/fiberglass blend shingles. Asphalt based
or organic shingles, although still popular, make up only about 10
to15% of the shingles sold today. An organic shingle is made up of
layers of heavy roofing felt (made from organic materials such as paper
or wood chips) that are saturated with asphalt. A thick coat of asphalt
is then added to the saturated felt. A layer of ceramic granules or
opaque-rock mineral granules are then added for color and for weather
and sunlight resistance. Asphalt/fiberglass blend
shingles are
manufactured in much the same way except that a fiberglass sheet is used
in place of the felt. The advantage of asphalt/fiberglass shingles are a
lighter weight shingle coupled with a longer limited warranty period and
a greater fire resistance due to the fiberglass content. The use of
fiberglass or organic shingles is a rather controversial issue among
roofers. Many of the roofing companies that suggest and apply mainly
organic shingles seem to have been soured by the early trial and error
period in the development of fiberglass shingles, and the fact that
if applied improperly during cold weather they are susceptible to
cracking. There was a time when the fiberglass shingles being
manufactured were not of the best quality, but those days are long
gone. The fact that 85% of the shingles being manufactured today
contain at least some fiberglass content speaks for itself.
Tear-off vs. No tear-off- Many roofing
companies love to tear off roofing jobs when it’s not really essential.
Why? Well the answer is simple, MONEY. That’s right. Dollars and cents.
There is more profit tearing off and it becomes, all too often, a nice
add on to the sale. You will almost never hear me bad talk my
competition, but it infuriates me to see customers burdened with the
extra cost of a tear-off when it was not entirely necessary and they
were told by the roofing company that it was. Most local roofing
codes allow a maximum of two layers of shingles because of the
difficulty of chopping through several layers of shingles if there is a
fire. There is also the fact that manufacturers will not guarantee their
products if shingles are used to reroof over more than one worn layer of
shingles. A tear-off does give you the cleanest flattest look possible,
and upon occasion, on structurally unsound homes the structure simply
will not handle the weight. There are cases when the shingles are too
badly cupped and curled or when large areas of wood replacement is
required that a tear-off is the only option. Often times when a 3-tab
shingle will not cleanly cover a worn first layer, an architectural
shingle will. The rough texture of the architectural shingle will
often times provide the desired look when a 3-tab shingle will not.
Hand nailing vs. Gun nailing- I am often
faced with the question of; “Are you going to hand nail my roofing?”
This is usually followed by a explanation of how another roofing
company said that applying shingles with a air powered nail gun is
inadequate. Over and above the fact that this has come into play as a
sales tool, this is such a popular issue because a roofing nailer in the
hands of a worker that has not been properly trained in its use is not
always a effective tool. All employees of Jarvis Exteriors are
required, depending on previous experience and on the job certification,
to hand nail shingles for up to three months. This teaches an employee
discipline and proper nail placement. If all roofers were properly
trained this issue would not exist. There are a few cases when gun
nailing is not effective, a few of these are; extremely cold conditions,
and on near vertical or mansard portions of roofs. Note: There are few
towns that require hand nailing on all roofing. I am seriously
considering attempting to change the no gun nailing policy of Crystal
Lake by proposing a roofing nailer training class that is open to
employees and owners of all roofing companies.
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