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# Building stairs- how much can last riser height vary?

#1
07-20-17, 09:43 PM
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Join Date: Nov 2006
Location: San Francisco, CA
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Building stairs- how much can last riser height vary?

We need to build a stair between a floor-to-floor height of 103". The max rise height per step allowed by code in our area is 7.75". So it looks like we will need to use 14 steps.

103" divided by 14 steps = riser height of ~7.357". If you round that to a 7 3/8" height per rise and build each step to exactly that height, then the last step would be 1/4" shorter than all the others. I'm guessing that is within allowable limits?

How far off can one step height be from all the others?

#2
07-20-17, 11:20 PM
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Join Date: Oct 2008
Location: New England
Posts: 10,514
Hi cruiser,
You can go with the 14 risers and just increase each 1/64th of an inch, about the width of a pencil line. Basically, the stringers are never built to that accuracy anyway. When I layout my master I calculate the length along the stringer and mark every step. Then you can set your rise and run with your rafter square. Fudge a little to get them all equal and there will be no 1/4" extra left at the top.

Bud

#3
07-21-17, 02:52 AM
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Join Date: Sep 2016
Location: USA MI
Posts: 6,525
You will have more variation just in the cuts, that is the rough in rough carpentry!!

#4
07-21-17, 03:34 AM
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Join Date: Oct 2001
Location: USA
Posts: 963
1009.7.4 of the IBC says you can have a maximum of 3/8" in any flight of stair. That said, I would split your 1/4" between the last 2 or 3 steps. You'll never feel 1/8" difference. But, like Marq1 said, if you can get that kind of accuracy with rough carpentry, you're doing pretty good!

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