stair support

[swimmer_spe]

I am building some stairs for my deck. How wide can you go before you need a 3rd stringer?

 

[Sparky617]

Here is a great reference, one of the most detailed I've found on the web. It is for Fairfax County VA and provides specs that will likely meet or exceed any local code. Their requirement for stair stringers is 18" OC unless you have solid stringers with cleats and 2x treads. See page 23. So in answer to your question they're pretty much required all the time.

Fairfax Co Deck Design Details

 

[Snoonyb]

Common sense; "pretty much required all the time."

 

[Sparky617]

Common sense; "pretty much required all the time."

Well if you wanted stairs to be 18" wide I guess you could get away with two. Per the attachment you can go 36" wide with a solid stringer with cleats instead of cuts and 2x treads. I'd probably only do that on a very short run of stairs to a deck a few steps off grade.