Stair stringers

I have just finished cutting my new stringers for my deck to ground which is quite long as the ground is higher where the deck is and slopes down to the level of the in-house garage. I have 13 steps...I made the sringers from 2x12x12 pressure treated wood. Here's the question...which I think I know the answer to...they are 39" from outside the left to outside the right so 36" between them. Should I be concerned about the length and should I put a couple of posts mid way? There is about 5" from the "V" of the cut so they are strong enough I think from what I read, but they sure do look awful long with nothing in between. Any one have a link to a site that deals with this? I have looked at a few sites but nothing deals with this much length. Thanks for any suggestions/help.
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JustBrowsing wrote:

Myself, I would use three stringers, not two, add a 2x6 or 2x8 cross piece between them and an additional pair of posts in the middle w/ cross bracing.
While they may well be "strong enough" w/o the extra material and bracing they will definitely be springy and will also have a tendency to sway/swing side to side in the middle.
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JustBrowsing wrote:

I think dpb is correct.l I recenly saw a quality carpenter double stringers for a long run. TB
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Double stringers, or at least a third one in the middle, and some cross blocking in a couple of places to create some box sections to stiffen the thing. But yeah, stairs that tall will have a little bounce. Also a long haul against gravity for some folks. On outside stairs that tall, most people put a landing. In wet weather, if you slip, that long flight will be a long way down.
aem sends...
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JustBrowsing wrote:

Agree with the others, a third stringer is needed. You could stiffen the stringers considerably by nailing a 1x12 skirt board along the outside of each (may look better also).
The next time you need to build stairs that high consider routing grooves into the stingers and slipping the treads into the grooves.
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If you have 5" remaining, you have slightly less than a 2x6 in strength, so you can look that up in the spanning tables. What are you planning on using for the treads? You almost certainly need a third stringer just from that perspective. When I built our deck, I actually used four stringers, because the minimum spanning distance on stairs for the composite decking I was using for the treads was only 12". I then put some X-bracing underneath the four treads and they are rock solid -- not even a hint of bounce on them.
Don't skimp on this, it won't cost much more in the grand scheme of things and you'll be happier if the deck and stairway doesn't bounce (our old deck swayed if you leaned up against the railing and wiggled-- our new replacement, which is quite a bit bigger, won't budge).
-Tim
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On 26 Sep 2006 17:01:34 -0700, "JustBrowsing"

My house is probably cheaper than yours, and I only have three steps and they are only 30 inches wide at the most (without my going to look) and the builder built the steps with 3 stringers, one in the middle. And maybe double stringers on each end. I'll check if you ask me to.
Now the thing is falling apart and I want to fix it up just for a year or two. I don't want the trouble to make or cost to buy 5 stringers. Nobody even uses it except me. Maybe I'll use two and redo the whole deck next summer or the next.
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