Minimum roof pitch

[dbags]

I am working on a home addition and I have a problem with the geometry of the new roof. I am trying to tie the new gable roof into the existing gable roof at 90 degrees (commonly called a cross gable configuration). The existing gable is very shallow so in order to tie into the existing roof below the ridge I need a new gable roof pitch less than 3. This seems very shallow and as I remember could be problematic for snow loads, ice buildup, etc... Can anyone tell me if there are good rules of thumb for minimum roof pitches for standard home construction. Also, is there a way to raise the peak of the existing roof to give me more height to work with for the new gable.

 

[DaveAtkins]

The issue is not structural; rather, most shingle manufacturers will not warranty their product below a certain roof pitch. I seem to recall that 3:12 is the minimum.

DaveAtkins

 

[IRstuff]

FWIW:

http://www.ornl.gov/~webworks/cppr/y2003/rpt/8391.pdf

TTFN

 

[JAE]

You can, if your aesthetics allow, have your addition ridge at a higher level than the existing. As the higher, new ridge approaches the lower ridge, you would have a small, triangular hip at the end that would transition down to the existing.

This triangular hip (perhaps only a few feet higher than the existing ridge) is a plane, on the same plane as the far side of the existing roof.

This is a very common way to do this.

 

[Ron]

JAE is right. Roof can intersect at any level, above or below current ridge line. You can also have different pitches intersecting, and you can have a different pitch on either side of a truss. As for pitch, if you are in a snow load area, I would probably limit to 4:12 pitch. If snow not consideration, then the limit for shingles, tile, and other mechanically fastened roof coverings is 3:12.

Your structural design can address any of the conditions, from flat to steep, so in that context DaveAtkins is correct that only the material warranty will make a difference.

To prevent heartburn later on, whatever you decide to do at the intersection, make sure it has proper flashing.