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BDU Cedar Roofing College™
Raise the Roof: Roofing Exposure and Pitch Explained
What you will learn:the definition of roofing "exposure"; the definition
of a roof’s "pitch"; importance of adhering to Certi-label instructions for
roofing exposure; methods of measuring a roof’s pitch.
When exploring the world of cedar roofing, two terms that are very important are
"exposure" and "pitch." What do they mean?
Before you can begin your roofing project, it’s a good idea to find out a few
things about your existing roof so you’ll know the scale of your project.
Knowing the right terms is therefore critical, as is also knowing how to
calculate the costs of your project. First, we’ll look at two essential terms
you should become familiar with before starting a roofing project: "exposure"
and "pitch."
Exposure for roofing
"Exposure" refers to how much of your roof is subject to direct sunlight, or
more to the point, to the area on the shingles or shakes that you leave exposed
in their overlapping installation. It could be argued that the less exposure
you have, the stronger your cedar roofing will be against natural enemies such
as UV rays, animal traffic, vegetative surface growth, and the every day
ravages of the weather. However, Certi-labeled manufacturers will specify a
maximum allowable exposure for each type of cedar shake or shingle. It is
extremely important to pay close attention to this information; if you exceed
the manufacturer’s recommended amount exposed area, you may void any applicable
warranties, and you may also subject your roof to premature leaks. Also
remember that going under the manufacturer’s recommended maximum exposure will
decrease your "square" coverage and increase the costs of your materials.
Within the limits of the prescribed maximum exposure for your roofing project,
however, the exposure area you decide upon is only limited to your visual
sense, and budget. Remember to allow for an additional five to ten per cent
wastage allowance. This percentage is a fairly safe bet after you’ve decided on
the exposure of your cedar roofing project.
How to measure the pitch of your roof
The term "pitch" in the context of roofing has to do with the slope of your
roof where the cedar shakes or cedar shingles are to be laid. Calculating the
pitch of your cedar roof involves calculating the ratio of how much your roof
will rise in relation to how many inches it runs horizontally. For example, if
you have a 8/12 pitch, it means that for every 12 inches of horizontal
distance, your roof will rise by 8 inches. Obviously, this will effect how much
cedar roofing you will require for your project, so it is necessary to
determine the pitch of the roof before you start shopping for roofing
materials.
If you have the original building plans for your house you should be able to
able to obtain the roof’s pitch. Otherwise you may wish to hire a roofing
specialist to determine the pitch and your total coverage area. If you choose
to make the measurements yourself, you should possess the skill in handling
levels and tape measures as you will have to do this while in an awkward space
or position. If you know how to use specialized equipment such as a surveyor’s
transit or modern electronic surveying devices, you might be able to obtain one
to more quickly determine the pitch of your roof. If you are not a professional
builder, however, you may find all this too complicated, and there are other
relatively simple methods open to you.
You can get a reasonably close measurement of the required distances from
inside an attic under the roof, or if outside, from a ladder beside the roof.
However, safety should be a concern since you will be on a ladder or standing
on a rafter inside your attic. If you are unsure of yourself when it comes to
working on a ladder, call a professional roofing contractor to help you.
Now that you are armed with the language and the knowledge you need to start
your project, it’s time to start turning your vision for a new cedar roof into
a reality!
Back to Roofing College
©2009 by BuildDirect.com Technologies Inc. (BuildDirect™). All rights reserved.
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• Mark at spot on the bottom of your carpenter’s level that is 12 inches from
one end (A).
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• Standing on a ladder so you can reach at least more than a foot up from the
bottom of the roof, place the bottom edge of the end (A) of the level against
the roof.
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• Hold the level in one hand so it is in fact level as it sticks straight out
from the roof. (Imagine you can see a rafter protruding from your attic at the
base of your roof. Your level should be parallel to the imaginary beam.)
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• Using your other hand to hold a tape measure (a string will do) at the
12-inch mark on the level, measure the vertical distance from the level to the
roof.
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• As a fraction, put the vertical measured distance (inches) over 12.
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• The resulting ratio (e.g. 8/12) is the roof’s pitch.
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• Mark at spot on the top of your carpenter’s level that is 12 inches from one
end (A).
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• Standing on a rafter so you can safely reach the roof (or one of its
supporting rafters), place the top edge of the end (A) of the level against the
inside of the roof (or the rafter).
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• Hold the level in one hand so it sticks straight into the attic space from
the roof’s inside surface or the surface of the rafter. (The level should be
parallel to the floor, or imaginary floor, of the attic.)
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• Holding a stiff tape measure in your other hand, measure the vertical
distance (inches) between the 12 inch mark on the level and the inside of the
roof (or rafter).
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• As a fraction, put this measurement over 12.
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• The resulting ratio (e.g. 8/12) is the roof’s pitch.
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