On Sun, 10 Aug 2008 21:56:06 -0700 (PDT), stratford1
wrote:

I'm building a set of stairs on my deck and CANNOT seem to find a
straight answer on this. I'm using closed outside stringers spaced 36"
and will use metal tread brackets to attach two 2x6 treads for each
stair. Some info I've found says I DO need a third stringer in the
middle for support...others have suggested I DO NOT need a third
stringer as long as my span isnt longer than 36". Any suggestions on
this? Will my 2x6s hold up ok or should I do the third stringer
regardless to make my stairs stronger?

Sounds wide, I'd use a middle stringer.