Central California's
Roofing Experts
The slope or pitch
of a roof is the
degree of roof
incline expressed
as the ratio of the
rise, in inches, to
a run of 12 inches.
For example, a
roof that rises 4
inches per foot of
horizontal length is
described as
having a 4/12 slope.
A slope that rises
18 inches for every
foot has an 18/12
roof slope. A general
rule: The smaller the
first number, the lower
the roof pitch.

The degree of roof incline ––slope–– is a key factor in determining the type of roofing
material that should be specified. The normal application range for shingles is between
slopes of 4/12 and 21/12.

On slopes at or below 2/12, shingles should not be used. With low slopes, water can back–
flow under shingles, and the area can be difficult to ventilate or insulate effectively. Only
products like EPDM (rubber) and SBS (modified bitumen), specially designed for low slope
applications, should be used.

Shingles can be used on slopes between 2/12 and 4/12, but only if two layers of
underlayment or a waterproof moisture barrier is used beneath the shingles.

On slopes greater than 21/12, special techniques for sealing the shingles must be employed
because steep slopes create a higher potential for shingle blow–off and/or slippage.
Do you have
questions about
your roofing project?
Click Here to
see Comments
From Our
Proud Member Of
The Following
WARNING: Chemicals
known to the State of
California to cause cancer,
birth defects, or other
reproductive harm are
created by the combustion
of propane, use of hot tar
kettles and tar products.

Our industry is required to
comply with Proposition 65
known as the California
Heath And Safety Code. We
are required to give you
this warning.
What you
Need to
know about