I've been reading this forum for a couple of years, as I'm involved in a project to build a small off-grid home in Ontario. I'm posting now, for the first time, in the hope that someone might be able to give some general tips on how best to do a cantilevered roof. I'm attaching the drawings -- a floor plan with dimensions, and then an elevation that shows the general shape/character of the home. What we are hoping to do is have an 8-foot cantilever. Does anyone have a sense of how we might pull this off? Sincere thanks for any help. p.s. Sorry for the poor quality of the photo -- I had to reduce the size/quality to meet upload limits.

This is the other picture.

You should have posted the side elevations so we can see the profile you are trying to accomplish. A truss company would be able to make a "scissor" type truss for your covered deck area in that shed roof profile but you would lose a little height at the peak, they may possibly be able to engineer a flat truss that could span your structure and cantilever the 8' in the orientation your sectional shows. Otherwise my first thought would be to frame the porch wall with the door all the way up to reduce your span, cantilever a steel beam or lvl at the peak and use top mount hangers with deep I-joists or wood floor trusses as rafters, looks like it would be maybe a 28' run, if you couldn't make that span you would probably need to look at steel if you were trying to keep the roof assembly as thin as possible. Usually you will see lvl beams or glulams cantilevered with the roof structure on top of that.
An engineer is what you need.

retro;

 

usually cantilevers are 1/3 out 2/3 back....8ft. is extreme , I would get some engineering or your LVL supplier may help......gratis

thanks Chris and Greentree. Greentree, you're right that the goal is to keep the roof assembly reasonably thin....we don't want a big mushroom cap on the top of the house. I think we're off to get an engineer.

Just an update on this, for those interested. The structural engineer basically said: No Problem. Load tables in the Ontario Building Code are hugely conservative because they are designed for homeowners/gumbies. We can apparently do either: i-beams (engineered lumber) on 24 inch centres, or take two 18 foot 2 x 12s, scab them together so they overlap and form a total length of 26 feet, and set them on 24 inch centres. He said he would have to crunch the numbers to be 100 % certain, but was pretty sure of this. (I should mention this is no flake...he teaches at a major uni and works for a top-notch structural engineering firm). So this was all a huge surprise, and excellent news.