cantilever joist

giglotti007

iam lifting the front part of my severely sloped roof and building up the front wall 8 feet with a 5/12 pitch. want to cantilever out 18 inches how far back must the joist go to carry the load.
and i cant sister the joist because they run the horizontal any help
if i can get the joist 4 feet in the the house what can i get in inches to cantilever.i am using 2x12s

Ron6519

Need a little clarity with this post. The terminology you're using seems incorrect.
Are "horizontal" joists ones that are actually parallel to the porch wall? Because by definition, joists are horizontal. Wall studs are vertical.
Post a plan or some pictures of this situation. I'm confused about the, "iam lifting the front part of my severely sloped roof and building up the front wall 8 feet with a 5/12 pitch."
Ron

mrgins

The general rule of thumb is that for every foot of cantilever, you have to go back two feet into the structure. In your case, however, I would go the full four feet as you are carrying the roof load. Are your existing joists 2x12? I doubt it, but maybe they are. You need full access from above or below the joists, and doubled up cantilever joists to support the existing joists you will cut. You'll also need double and single joist hangers in the appropriate places.
As this thread unfolds, we'll gain more info to help you.

Octopus

Generally, one third out ( cantilever ) two thirds in. There are exceptions.

For example, I would not cantilever a 16' 2x4 5 feet or even a 2x6 for that matter. A 2x12 is fine.

If you go 4 feet into the structure you can cantilever 2 feet

Anyway, it sounds as though you are building a cantilevered floor ( 2x12's ) and you will be building three exterior walls on it? Is that correct?

If so, which of the walls are bearing the new 5/12 pitch roof?