Hi all. New here. I looked at the other forum sections and not really sure where to put this, so I put it here. Sorry if I am in the wrong category.
I am considering a remodel project. Well, technically I am beyond the considering part of it since I ripped down the old structure already. I had a 13'6" x 23' 3" 3 season room. Nothing special about it. It was built on a 12in thick cement slab amd it was bolted down to the pad with pressure treated 2x4 construction. There were 2x4s run along the perimeter to give a place to tack on t-111 siding and topped with screen that was crudely stapled into place to prevent bugs while still giving a nice atmosphere to stay out of the buggy backyard and also provide shade. The structure was mounted the the eaves of my garage and had a shallow roof pitch of maybe 1/12 or possibly 2/12 pitch at best. The person who built it, built with a steel roof that had an offset (drop where the 2 rooflines met) of about 1 ½ inches and the steel roof didnt butt up to the garage eaves leaving a small gap that leaked with every rain storm. The longer it rained, the longer the floor had standing water on it. Keep in mind that the garage roof is a fairly steep pitch, but I'm not sure of the pitch currently. The previous owners had run a piece of rubber flashing tape along the seem to deter the water from making it to the seem and it was not working very good. Long story shortened, I took the steel off, raised the 3 season roof to meet the garage roof, flashed and put ice and water roughly 2 feet up the garage roof and the remainder onto the 3 season roof. I then flat roofed over plywood and I still had a leak where a valley comes down to a inside corner. The fix was only supposed to be temporary to get us through until we could afford the cost and time to redo the room as an official 3 season room, complete with doors and windows.
Fast forward to now. I am in the planning portion of the remodel. The though process I had, was to change the roof line from a shed dormer style roof, to a gable end with ridge beam, etc.. I have done several sketchups regarding the remodel and I am in a little bit of a quandary. The garage is essentially a gable end with ridge beam going 90 degrees from the main roof. The 3 season roof will come off of the garage roof almost centered and will be facing the same direction of the main house. There is already a valley on the roof of the main house where it meets the current garage roof. If I do this style roofline listed above, I will end up with 2 valleys that will meet very near one another. My fear is that I will create a crotch like area where snow and ice will dam up and then back up the roof. Is there a minimum distance that 2 roof valleys should be spaced apart to prevent the damming? Thanks for any help. Bob