The safest way to determine the pitch of an existing roof is to measure from inside your attic using a level tape measure and pencil.
Minimum lean to roof pitch.
Regular asphalt shingles that are rated for 4 in 12 roof slopes can be installed on lower slope roofs by simply installing a waterproof membrane under them.
There are advantages and disadvantages to having a steep pitch versus a shallow or low pitch.
Solutions for lean to sheds.
However you can only use this pitch with built up roofing or specialized synthetic roofing.
The minimum roof pitch for shedding snow is around 30 or a 6 12 or 7 12 slope although this is not a definite as the material of your roof the direction of the snow and wind are some factors that can affect whether or not snow will slide as roofs of as little as 10 have been reported to shed snow.
The minimum roof pitch is also subject to the standards set forth by the various building codes used in the respective regions.
Importance of a roof pitch.
If you are building a new roof however consider the climate to determine the correct pitch and proper materials.
The minimum slope of a roof depends on the roof s profile.
Express the slope of a metal roof by a ratio which indicates the pitch of the roof.
You need to consider the slope requirements of each panel to determine this minimum slope.
Both the asphalt shingles and metal roofs can be installed on a low slope lean to shed roof if the proper product is used and it is installed properly.
Simply put pitch is expressed as rise over run just as the grade is simply this fraction expressed as a percentage.
A 4 12 pitch being 4 inches of vertical rise over one foot or 12 inches of horizontal run.
The profile is the shape taken by the sheets when you bend them to form panels.
In roofing it is expressed in inches of vertical rise over inches of horizontal run.
The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.