Determining Roof Pitch

Roof pitch is determined by finding the amount of rise per foot run. If you are framing a new home,
garage, shed, or similar building the pitch of the roof can be obtained
by looking on the plans. It is represented by a triangular shaped
drawing and expressed in inches, 4/12, 5/12, etc. the higher the number
the steeper the pitch or angle of incline.

When building an addition it is often necessary to tie the new roof into an existing one. In order to tie the two together the existing pitch must be known.

Find Existing Roof Pitch

New Roof Framing Forum

The easiest way is to use a tool called a pitch finder that
can be placed on top of the roof, on gable end soffit, or in the attic
under a rafter to find the pitch.

This is a special tool and can also be
used to find level, plumb, or any angle in between.Another method is to use a level and framing square from on top of the roof.

Place a framing square on the up hill side of the roof with the body level and the tongue facing up.

Place a carpenters level in the plumb position against the roof and the tongue of the square.

Keeping the level tight to the roof surface, the tongue of the framing square, and the body of the square tight to the roof move the square and level around until the level reads plumb.

Make a pencil mark where the heel of the framing square meets the level and measure this distance. Divide the measurement in two, the answer is the pitch.

You can also use a level from under the soffit on a gable end to
find the pitch. This technique also works well for figuring the angle
cuts on siding.

On a ladder and under the soffit make a level mark from the soffit towards the center of the gable.

Measure 12″ from the soffit along this line and make a mark.

Plumb up from the 12″ mark until you run into the soffit again and measure this distance, this is the pitch of the roof.The
pitch can also be determined from inside the attic provided the common
rafters are 2 X 8 or larger with the use of a level and speed square.

From inside the attic make a plumb line on the side of one of the common rafters.

Align a speed square along this plumb mark and read the pitch along the common rafter scale.

Roof Pitch Chart

Use this pitch chart to give you an idea how steep a roof is when someone says the pitch of the roof is 4/12 or whatever it is.

Tips on Roof Pitches

There are several factors to consider when deciding upon a pitch for a new roof
such as geographical location, aesthetics, and cost. In general the
steeper the roof the more it will cost to build and maintain, but the
roofing material will last longer before needing replacement.

Low Pitched Roofs

Are so called when the pitch is below 3 1/2. Though easier to work on and cheaper to construct asphalt shingles should not be used on lower pitched roofs. They require special roofing materials and will need routine maintenance more often.

Medium Pitched Roofs

This pitch range is between 3 1/2 and 7 1/2 and makes up the bulk of most new roofs
in America. A pitch of 4 to 6 is the pitch I would recommend to anyone
building a garage, shed, or similar building. These roofs can be walked
safely by an average person and require no special equipment.

Steep Pitched Roofs

Are anything above a 7 1/2 and require special equipment to keep
roofer’s and material from sliding off, but will last longer than lower
roof pitches.

Links to Related Carpentry Pro Framer Pages

Roof Pitch to Home Basic Roof Framing

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