# cutting PT 2x12 stair stringers



## rogerm (Jun 27, 2012)

I'm adding stairs to my deck which is 6' above ground. I cut the first stringer from a PT 2x12 12' long. The next day I see the cut stringer is bowed. Will this straighten out when I attached it to the deck? Or is there a special way to cut a stringer to prevent this from happening?


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## Dave Paine (May 30, 2012)

PT lumber is normally wet from the treating process. Some pieces will bow and warp when you get them home.

By cutting the stringer do you mean cutting out the "V" for the steps?
How much continuous depth is left in the board?
How much bow?

I do not expect this will correct itself. If the bow is not too bad and you are able to use the stringers with the bow in opposite directions, you will likely be able to clamp the boards straight while you attach the stair treads.

The last time I did a PT stair, I routed grooves in the stringer so I did not have to cut it, and then screwed in the stair treads. This held well, but the wood is getting to the replacement phase after many years.


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## Steve Neul (Sep 2, 2011)

Probably the problem is with the board and not what you did. More than likely it won't straighten out. I would just cut a new stringer from a different board. It might help if you propped the board up verticle so air could get to both sides. Warpage is either from the board not being seasoned well or the moisture content on one side was raised more than the other. Sometimes if you leave a board laying on a flat surface where air can't get to one side, moisture from the air can get into the other side making it warp.


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## woodnthings (Jan 24, 2009)

Dave Paine said:


> The last time I did a PT stair, I routed grooves in the stringer so I did not have to cut it, and then screwed in the stair treads. This held well, but the wood is getting to the replacement phase after many years.


Housed treads like these will help prevent warping. The stringers are laid out convex side inward so the ends can be clamped up more easily:


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## rogerm (Jun 27, 2012)

*cutting PT stair stringers*

Thanks for the suggestions. After cutting the "V" for the stair treads, the stringer bowed probably 3-4 inches over 10'. There is 5+" between the cut and the uncut side of the 2x12. I was planning to attached a 2x4 along the uncut edge of the stringer for additional support. Maybe that will reduce the bowing.


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## cabinetman (Jul 5, 2007)

You could possibly pull it back to straight when installing the treads. Will there be risers on this project?













 







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## rogerm (Jun 27, 2012)

I will be using risers. Right now my stringer looks like a smiling jack-o-lantern mouth.


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## cabinetman (Jul 5, 2007)

rogerm said:


> I will be using risers. Right now my stringer looks like a smiling jack-o-lantern mouth.


With treads and risers you have good cross strength to hold the stringers straight.









 







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