Minimum Roof Pitch For Dormers

Thus a 4 12 pitch would be a 33 slope.

Minimum roof pitch for dormers.

You should have at least an 8 12 pitch for it to look as if it belongs. That pitch is too shallow to hold the shape of the dormer. It would end up looking very long and awkward. However rise over run is more efficient and easier to understand for the average diyer.

You can also divide the rise over run multiply by 100 and get a percentage. A shed dormer on the other hand is usually had on homes with a roof pitch of at least 8 in 12 or steeper. Having a steeper pitched roof allows for more space in a shed loft. The ideal scenario is if you can stand upright in the centre of your loft and raise your arm above your head without crunching your hand on the inside of the roof.

Pitched roofs can also be used to incorporate roof lights angled in a specific direction or dormer windows. A 4 12 pitch is around 18 5 degrees but not exactly. However you can only use this pitch with built up roofing or specialized synthetic roofing. The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.

This image shows a relatively shallow roof pitch of 15 degrees.