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.
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.
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.
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.
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.
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.
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.