Hi All Not sue if this is where I should ask this question, f not I appoligize.st bought a summer house in Northern Maine (130 inch snow fall annual)and the back of the house, (facing a lake) has a 4/12 pitch and a upper deck that is 10 feet wide and 7 feet out towards the lake. I want to extend my roof over the deck but to continue the pitch i will only have about 62 inches head height at the end of the deck, if I install a 3/12 pitch over the 4/12 then i will have aprox 76" head height. i only want the new truss to be supported by the roof with no columns attached to the deck. what would be the best way to seal the 3/12 to the 4/12 roof? I hope i explained it ok if not please ask me for any more inf larry

So the snow will now build up deeper at the change in slope. I'm unclear what is holding up all this snow load if there are no columns, but I think your best bet is to contact a local structural engineer who can help you figure out how to do what you want to do safely.

I agree with Bob, you would be wise to engage a local knowledgeable contractor/engineer to guide you on this project. In our area, we typically like a minimum of 6/12 in our high elevation areas that get a lot of snow. We also like metal standing seam roofs with synthetic underlayments to help protect against ice dam damage.

Deleted duplicate response.

Yep, snow is heavy, wet snow is catistrophically heavy... I don't see 10' of cantilevered roof with your snow load. It will almost certainly require upright posts at the deck edge, and perhaps replacement/augmentation of the existing deck supports to handle the additional roof load...

4:12 to 3:12 isn't a big difference in load - but cantilevered 7' out is. Ask your structural engineer about using steel (because you don't have much depth).

Thanks for the reply all. I currently have a house I built 6 years ago with a 6/12 pitch and the roof is canter livered 7 feet over my deck with no supports. The truss was designed to handle the weight, plus it is a metal roof so the snow slides of easy. The house I bought for my mother in law unfortunately has a 4/12 pitch and I need to go to a 3/12 to have head height at 7 feet. I am not worried about the load, that is easy. I am concerned about sealing the transition correctly not to have leaks as the snow will not roll off as easy as 6/12. Thanks Larry

maybe this:

Thanks for the response Larry

I think you have it backwards. The flash detail for a pitch change can be had by many metal manufacturers much like the detail above, with a high temp self sealing underlayment as last defense. With a 3/12 pitch or less manufacturers will start to warranty only certain products, generally taller concealed seams or standing seam only and the panel supplier will detail everything.

Your concern should be cantilevered load unless you're leaving details out. You cant just add on to a truss similar to a designed cantilever truss without careful design. Your 6/12 cantilever you had before had a designed bearing point and alot more height at bearing, the webs were in a specific configuration. Im sure you could redneck something and say i told you so, or maybe you are an engineer asking a question very unlikely for an engineer to ask, but a 3/12 7' cantilever off a 4/12 roof done right requires an engineer, probably involving steel.

Sure, it can be done. BUT you would have to tear of the existing roof and build the cantilever into the WHOLE truss, not just a simple overlay. That's what would have been done on your 6/12 pitched 6 year old house.