You can assess this in two ways either as the roof pitch angles which the rafters make with the horizontal or the proportion between the run and the rise of the roof.
Pitched roof slope angle.
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.
A 4 12 pitch is around 18 5 degrees but not exactly.
Pitch angle incline slope they all can be used to refer to the steepness of a roof.
On blue prints architects engineers usually display the pitch of a roof in the format shown on the image where number 4 represents a rise and number 12 represents a length.
Thus a 4 12 pitch would be a 33 slope.
A ratio is the most common way of expressing roof pitch or roof slope but degrees are also possible.
In the roofing trade the go to term is pitch and it is expressed in terms of 12 inches so the pitch of a roof is determined by how many inches the slope rises for every 12 inches it runs horizontally.
Roof pitch refers to the slope which the rafter creates.
Often you express roof pitch as the ratio between the rise and the run in the form of x 12.
You can also divide the rise over run multiply by 100 and get a percentage.
Roof pitch and corresponding angles.