Hello all,

I’m new here and I’m in the planning phase of a big renovation on a cottage. A bit of background, I want to take on the role of the general contractor/do as much as possible myself. I’m a DIYer and the most complicated job I’ve done myself was a kitchen remodel but I find myself pretty resourceful 😉 

I am located in Southern Ontario. Please take a look at the attached photos as it will help visualize things. The main cottage is the front section and the rear is a big concrete structure for boat storage. The cottage is 20 ft by 32 ft. It was built in the 60s/70s and sits on cement blocks with 2×6 beams and joists. The walls are 2x4s. The concrete boat house is essentially a concrete box. I’ve attached a screenshot of what I want to do, essentially a shed roof that starts in the front and slopes up above the boathouse to create a second level (would only take up a small section of the boat house roof similar to the screenshot. 

The plan is to keep the walls in place, including the sheathing. After tearing the roof off, we’ll frame up triangular wall extensions to fit below the shed roof. I was thinking a 3/12 or 4/12 roof which will give us enough headroom once the roof gets to the boathouse. For the framing of the roof I was thinking about using 24′ long lumber that spans the width of the cottage which is 20ft (no middle support). It seems like if I were to frame this myself with some buddies this is the most straight forward. My question is what the spacing and dimension of those rafters/ceiling joists should be. From reading the code , it seems like 2×8 12″ OC is just cutting it for this type of span but I’m not sure if there are additional considerations for snow load and this type of roof. 

If anyone here has some insight on what I’ve asked above or some other considerations you think I should consider please let me know!