A 4 12 pitch is around 18 5 degrees but not exactly.
Minimum roof pitch for dormers.
However rise over run is more efficient and easier to understand for the average diyer.
This image shows a relatively shallow roof pitch of 15 degrees.
A shed dormer on the other hand is usually had on homes with a roof pitch of at least 8 in 12 or steeper.
The loft space would be much larger with a roof pitch of 45 degrees.
Having a steeper pitched roof allows for more space in a shed loft.
Thus a 4 12 pitch would be a 33 slope.
Pitched roofs can also be used to incorporate roof lights angled in a specific direction or dormer windows.
Roofing gutters and all waterproofing anywhere minimum roof pitch i am planning a shed dormer with a roof that will have about 3 12 pitch.
The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.