Can anyone point me to a reference for stair stringers? How long can they be before they need center supports?
Thanks.
not sure of a spacific reference, but your on the right track. i’d call it out in need of support. i usualy go with a mid support for any stringer longer than 6 feet on “free floating” stairs and 10 feet for ones on a wall. some one will be along shortly with reference, please stand by…in 3…2…1…
It depends on:
The width.
Presence of a center stringer.
Whether or not the stringers are doubled.
Whether or not the cuts are overcut into the wood thats left.
How many knots and defects are in the wood.
Looks like the handrails are unsafe too.
Also is that just a single girder joist on the left with a 2x2 ledger?
It should be double thick plus the ledger.
Looks like low headroom too.
So it’s a judgement call? Seems like there would be a ‘code’ for it.
Were the stairs bouncy or wobbly?
If so, I would recommend additional 4x4 posts (with footings) be added in at the center of each stringer.
I don’t like how they put that 4x4 support inside the stringers on that pic David
all I can find in IRC is “A flight of stairs shall not have a vertical rise greater than 12 feet betwen floor levels.” Just off the top of my head that would be an 18 or 20’ stringer I think.
I always support mine somewhere mid span just to make them a bit more stout.
It appears that if the (meat) left after the cut out has been made, there is still 3 1/2" left, it meets the Code, but this stringer seems to exceed the 7 3/4" riser recommended.
Besides the fact the the railings do not meet code, and the stringers whether doubled or tripled for a 3 foot stair which is not apparent in the photo, I would recommend a 2 x 12 for a stringer with no intermediate support or in this case have one installed due the illusion that it looks quite flimsy.
What was the riser height of these stairs? And what was the tread width? This information would give me the calculation information required for a better conclusion.
Marcel 
I’m sorry that I didn’t take the measurements that I should have. The stairs felt firm enough. Here’s what I said in the report about the stairs:
"Outdoor stairs to rear deck have no balusters. A child could easily fall to concrete below. Recommend balusters spaced no greater than 4 inches apart.
Deck stair stringers are 9 feet long without center supports. While the stairs seemed firm, a better installation would have central support posts. "
Gee Dave, those stairs seem a little skinny. i think they need a little something, like uh, oh yeah TREADS. that otta do it.
Dave, the guard rails seem unsafe too.
:mrgreen: oh wait, on second look i see one tread half way up, incase you need a rest i guess.
Case the stairs, end of problem.
Larry