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My walkout basement concrete pit was poured with a 36" wide area for the steps you can walk up to get to grade (sorry for the crude ASCII art):

  w
+---+
|   |
|   +--------+
|            |
+------------+

w = 36" wide. It currently has wood stringers that are now rotting.

I'd like to replace that stair system with angled steel cleats bolted to the concrete on each side of the pit, and then span 36" 2x12 treads from cleat-to-cleat.

What thickness of angled steel should I use?

alfreema
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    Not sure where you're located, but in the US all of the big box stores sell galvanized stair cleats made by Simpson, USP, etc. – SteveSh Feb 19 '22 at 15:36
  • 3 or 4 tapcons per side (so... maybe 60 holes) would be pretty time-consuming and bothersome to do accurately in concrete. I'd consider PT stringers and then regular screws and Simpson TA10Z (12 gauge, for what it's worth). – Aloysius Defenestrate Feb 19 '22 at 15:45
  • Well, gosh that makes it easy. After checking one of the box stores, I found a Simpson TA9Z-R. Any idea if that can be bolted to concrete instead of a wood stringer? – alfreema Feb 19 '22 at 15:46
  • And don't skimp on the tread thickness... code would require a central stringer. – Aloysius Defenestrate Feb 19 '22 at 15:47
  • @AloysiusDefenestrate I don't mind taking the time to bolt in cleats. I want avoid stringers for a couple of reasons. I'd use wedge anchors instead of tapcons. I just want to make sure the cleats won't corrode if against concrete instead of wood. – alfreema Feb 19 '22 at 15:48
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    My faint recollection is that you can get a 1/4" lag/sds through those hangers, but you'd have to check. – Aloysius Defenestrate Feb 19 '22 at 15:50
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    Simpson Zmax is fine against concrete. – Aloysius Defenestrate Feb 19 '22 at 15:51
  • @AloysiusDefenestrate perfect. I'm going to double check 1/4" red hedge wedge anchor sheer loads -- should be perfect with those hangers if they have 1/4" holes! – alfreema Feb 19 '22 at 15:53
  • Stringers last for 100y. Cleats you get 20 if you're lucky if it's exposed, and you have to plot it. If you didn't get an A in geometry.... My set of bilco doors has three pre cut stringers, and it took an afternoon. With cleats, somewhere it'd be wrong, and it'd've took forever. And when the day comes to pull the staircase to get back there, I'm pulling the whole case, not abusing the thread's screw holes. - Made the mistake of doing an entire four-flat's deck with these. It's on its second set *of replacements* and it's not even 20yo yet. – Mazura Feb 19 '22 at 16:24
  • The treads aren't particularly happy about having their 1/4" lags taken in and out six times. And once the heads rust it gets real fun. – Mazura Feb 19 '22 at 16:29
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    I would agree with @stevesh , I would never use tapcons on a live load like this something more like a 1/4” x3, red head or expanding steel anchor, these will probably outlast any pressure treated wood steps a few times over. – Ed Beal Feb 19 '22 at 18:33

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