I am adding a two story addition to the rear of my home (which is a colonial brick home 36 ft wide & 24 ft deep). The roof is side gabled and has a 7/12 pitch. The addition will be centered in the back and run across the entire back of the house. The addion will be 36 ft wide & 18 feet deep. The gable is directly centered to the existing house. The top of the roof of the addition will run to the top of the exsiting roof and the bottom of the addition roof will run to the bottom of the existign roof. I am trying to determine the pitch of the roof of the addition and I am concerned that the pitch will be too flat and look bad (my draftsman does not agree). Any thoughts on how to determine the pitch? Will it look too flat and look bad? Thanks in advance for your help.

I am assuming that your new addition is to be a gable with the ridge running perpendicular to the existing ridge. You have a 24 ft depth now and a 7/12 pitch. I would figure that means you have a 12ft run with 7inch pitch which gives you 7 feet of rise. Take that 7 foot of rise, figure 1/2 of the 36 ft span gives you 18 feet of run, 7ft of rise so you get a pitch of 4 21/32 . I don't usually respond, but I saw that you didn't have an answer yet. It is a simple calculation on the Consturction Master series of calculators. ( you need one with the rise/run buttons.) The roof is a little flat, but less than 3 pitch from your original roof and it is on the back of the house anyway. If that handles your snow load, I would go for it. By the way, the new ridge length is 30 ft (plus overhang) and a valley rafter of 26 ft 5 inch or so. Hope that helps