[Clutchcargo]

Typically you would use a plywood hanger board to attach the stringers to the joists as depicted below. The problem is, my joists are only 2x8s. Can you still use this hanger board method?

[Willie T]

I'd like you to imagine yourself jumping up and down, heavily, on that top step. Do you see how that plywood might tend to fold back under at the lower portion? And at the same time, begin to pull apart up by the floor level?

I think you could curtail this action by screwing and gluing in some 45° (or actually the angle of the stairs, not really 45) blocks of 2 x material right where the stringers are.

Wouldn't hurt to square off the upper back corners of those 45's and install a 2 x 4 ledger across the stair opening, snug up against those angle blocks so they can't shift rearward. Kind of like the 2 x that is affixed to the floor to keep the bottom of the stairs from sliding forward, the thrust plate. (Left drawing)

Of course, if you are able to actually extend the rear portions of those blocks up into the joist cavity, you could nail them to the sides of the joists..... but they would have be solid enough to brace the top ends of the stringers solidly from behind the plywood... and your joist layout may not be suitable for that. (Right drawing)

The whole idea of what I'm suggesting is to keep that plywood straight, flat and solid.

[Scuba_Dave]

I guess no chance of installing a 2x support under the top end of the stair riser? I'd never use OSB, maybe 3/4" plywood
Then use some metal hangers - securely nailed into the joist

[Willie T]

Originally Posted by Scuba_Dave

I guess no chance of installing a 2x support under the top end of the stair riser? I'd never use OSB, maybe 3/4" plywood
Then use some metal hangers - securely nailed into the joist

I durn sure agree with using good ¾" plywood, or better yet a 2 x 10 or 2 x 12, but not OSB.

[Scuba_Dave]

Another thought is to add another 2x6 directly under the existing 2x8 floor joist. Attach it to the 2x8 floor joist with metal plates. Then go over both joists with the 1/2" or 3/4" plywood

[Clutchcargo]

Yes... no OSB, I just used that pic to help me illustrate my problem.
I had a feeling that it would not be the best way to assemble. After some more research, I found that I can move the joist back a few inches and incorporate a few inches of the top landing into the stringer. The stringers would attach like the pic below.

[Scuba_Dave]

The top step of my stringers is even with the 3/4" sub floor
So my stringer lands fully on the joist
I left enough 3/4 sub floor so that will cover the string & all be one piece
So very much like the pic
Top joist that it hangs off of should be doubled

[Willie T]

Originally Posted by Scuba_Dave

The top step of my stringers is even with the 3/4" sub floor
So my stringer lands fully on the joist
I left enough 3/4 sub floor so that will cover the string & all be one piece
So very much like the pic
Top joist that it hangs off of should be doubled

Sometimes the architect insists on a flush landing, but I also prefer to build stairs the way his last photo shows. I think it even looks better, and no doubt I feel better about all that stringer end resting way up there on the joist beam.

[Clutchcargo]

Thanks, this way makes me feel better about the structure. I like to build things that stand on its own even without fasteners.