How To Cut Stringers On 45 Degree Corner

I have the regular stringers figured out, but I'm having trouble figuring the doubled corner stringers. Do I just change the run? Is the tread width different?

The total rise is 32" and the run is 42" I'm using 1" boards for treads and risers. The calculated run for the corner is 45.4375. Also, how do I account for the 22.5 angle on the top of the stringer? The calculated run is from the center of the double.

That is a 22.5 degree stringer. If you divide your run by 12, and then multiply by 13, you will have the correct run.

There's a couple ways to do this.

The "cheat" method (involved no math) is to run your treads long, trace at 22.5 degrees, and theres your run.

There's also a couple ways to do it with math. Easiest would probably be figure out the lengths of the "triangle. The standard stringer being one side, distance from framing point of standard stringer to framing point of angled stringer being another side, and the angled stringer being the hypotenuse. Then it's just Asquared+Bsquared=Csquared. Divide your hypotenuse (stringer) by the number of runs on the standard stringer and you have your run the angled stringer.

When Roof framing, the 12 inch on a framing square is used for calculations of Common Rafters for a given pitch.
Use 17 for the Hips/Valleys of regular 90 degree corners.
And use 13 for Bay windows at 22 1/2 layout.

Whatever your regular stringer layout, convert it to a "12 Pitch" and use 13 instead of 12 for the 22 1/2 degree stringers.

Should work fine.

^^^ or use Warren's method above

You'll also need to bevel your risers 22.5 degrees.

You mean like this?

Nice teaser. Where's the finished pics?

I actually forgot to take finished photos! Stupid mistake as it turned out awesome. I have the go back to look at new job, kitchen remodel, I'll try to remember to take pics of deck.

Interesting framing.

Inspectors here would not like the decking being nailed to the 2 by's on the flat like that. They would want it supported by a stringer, which takes us back to the answers proposed above.

What are you talking about? Those are double 2x10's for the ledger and you can't see the carriage bolts that hold the stringers to the ledger. Also, all 2x4's are set into the notched stringers......how would that not be to code? The bottom plate is also sleeve anchored to the concrete pad. So there is no way the stringers can slide forward. It passed inspection easily and the inspector loved it.

I think he is talking about the flat 2x4 "treads" to support the treads on the diagonal portion of your stairs.

The flat parts are only to screw the decking into, the stair front is 7" and can support the load. The ends are resting on a sandwiched 2nd stringer cut to take the weight. There is no reason for a stringer, would be easy to make 1 and attach it but it is not needed.

I lay out the stringers like they were a hip using 17" on the framing square.
If the stairs are being a Ill lay them out with the square. Then make the plum and seat cut, tack in place and use a straight edge for minor adjustments in layout.
I use blocks behind the riser on the hip stringers. It helps me with nailing and adjustments for a nice tight miter.

The only thing you have to do is change the length of the run. Anytime you are dealing with an angle you must remember that degrees implies you are working with part of a circle. A circle has 360 degrees and you know the part of it you are dealing with. In your case that is 45. Do this: divide 360 by 45 to get a number. Divide this number by 4 to get another number. Whip out your smart phone calculator and find the square root of this last number. Multiply your standard run by this square root and you have your new run. Works for any angle.

Sometimes you will run into some really weird requests. I was asked once to build a 7 sided gazebo with 3 riser steps all around. Every stringer was going to be a hip stringer. Here's how I figured out the run length and tread angle cuts:
Tread end cut angle = 360/2(total sides) =360/14 = 25.714 degrees = just under 25 3/4 degrees.
Run length multiplier = square root of (total sides/2) = square root of (7/2) = square root of 3.5 = 1.871 (multiply the standard run by this to get new run.)

I didn't need Trig or my ProCalc. Just my brain and a smart phone.

Slope gain on 22.5deg = 1.082.
Mulitply 1.082 x your std tread run, & you will get 45 stringer run lth.

Example, if you had a 10" std run:
45' stringer run =1.082 x 10 = 10.82.

Slope gain is your friend!

No, I don't know??? The 45* angle does not appear to be bisected by the double stringers.

What did the tread length of the cornered steps end up at? I'm guessing that if the standard side steps have 10" tread run stringer cuts, your 45* angled steps have a 7 1/16" tread run.

Maybe my old eyes are . . . . what's off?


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How'd that pass inspection? 7" tread w/ 7" riser?

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it's definitely a different way to get there.....the main problem lies in the finished product where the non bisecting gaps at the transition won't line up and will look... welllll..... like the transition in the above deck boards

sorry Birch ... i just took another look at that picturethat don't work !!!!!

If there is a lesson to learn from the deck in post #6, it is that working things out with a well drawn plan prior to construction is always a good thing. It generally appears that this may not have been the case with that deck. (i.e., Odd staggered break in the deck lines and the reduced Tread width, ). Luckily, the OP has/(or had) better plans.

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