Making A roof over existing Deck

[guskardasi]

Can someone tell me how to figure the roof rise when making a roof onto another roof?
iS IT CALLED ROOF RUN?
tHANKS
GUS

 

[1320stang]

not sure of your question. Rise over run would be something like a 4:12 pitch. Rises 4 inches over a 12 inch run. Most times, if you have to go up a roof pitch with a shallower pitch, 1/2 the main roof pitch usually looks best. 3 pitch on a 6:12 roof, 4 on a 8:12. Keep in mind if you go with less than a 3 pitch, it's not recommended to use shingles, hot mopped rolled roofing is better.