I have a set of stairs on a deck I am building that I am trying to stiffen up without putting a beam mid-span. There are a couple buried items that I cannot really navigate around including the septic main.
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Specs:
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Total Rise: 88â€
Total Run: 60â€
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Step Rise: 7.5â€
Step Run: 11â€
Total width of steps: 36â€
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# of Steps: 8
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Stringer: 2X12
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# of Stringers: 3
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I was wondering about bolting some angle or “C†channel to the inside of the outside stringers and on both sides of the center. I have about 5†of width in my stringer at the narrowest point.
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Any suggestions?
<!—-> BTW… Some of you may remember the curve deck project? It turned out great! I will post photos sometime soon!<!—->
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Regards,
WIT
Replies
I think you have your rise and run wrong. It should be reversed, no? (Step rise of 7.5 x 8 steps = 60" rise, not 88")
I think Nick is right. You have you rise and run backwards. Anyway if your rise is 60" you would have 8 risers at 7.5" with 7 treads. Using 2x12's for stringers is plenty strong. Your also using three stringers for a 36" width. Why do you think you have to stiffen them up?
I can't imagine what kind of loads you're predicting that would require a center stringer on a 36" wide, 2x12 tread; sounds like serious overkill to me.
To stiffen up the entire unit, try mortising the stringer faces to accept the treads instead of cutting the edge of the stringer as you describe in your plan. Using 2x12 stringers uncut, you will have plenty of depth in them to make that short staircase nice and sold with no mid-way support necessary.
Set the treads in the mortises with exterior-grade yellow glue or polyurethane glue, and run two ¼"x4" lags into each tread end through the outside of the stringer to tighten the whole thing up.
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
I tend to agree that don't need a mid-span stringer. Rather than mortising I would cut a toothed stringer and fasten it to a full 2X12 apron for the sides.I think it would be easier than a mortise.
If you are intent on beefing up I would use a center carriage and through bolt a couple of 2X6's, one on each side to it. Both of these approaches combined would require one more 2X12 and 2 more 2X6's and maybe two extra hours. But should produce a rock solid stair, enough for the fat lady to dance on.
Your staircase is going to be less than eight feet, so unless their is extenuating circumstances. Just a simple housed stringer is probably OK, either mortised or apron/stringer combined.
The best way to strengthen cut stringers is to not cut them, but instead mount the treads on cleats bolted to the sides of the stringers.
To keep the steps themselves from flexing install risers against the bottom of the treads. The riser need not be full height. Eg, a 2x6 riser would keep trash from building up on the treads.