# Porch stair tread span ?



## Arky217 (Aug 18, 2010)

Using treated SYP 2x12's for open stair treads (no risers), what would be the maximum span between stringers without excessive bounce ?
( just 2 stringers, no middle stringer)

I feel fairly confident 3' would be ok, but not sure about any wider.

Thanks,
Arky


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## gregzoll (Dec 25, 2006)

Your run can be as long as you want, but the rise between treads can not be any more than 7 3/4 inches. As for the stringers, depending on how long the treads are, I would go no more than 18" between stringers. Any more than 24", would see bounce, especially depending on the weight that you plan on carrying up them, or how heavy the heaviest person would be to ascend the stairs to get to the deck. Also keep in mind, how firm the deck is, due to stairs that bounce, your deck would have bounce in it also if not properly built.


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## Ron6519 (Mar 28, 2007)

Arky217 said:


> Using treated SYP 2x12's for open stair treads (no risers), what would be the maximum span between stringers without excessive bounce ?
> ( just 2 stringers, no middle stringer)
> 
> I feel fairly confident 3' would be ok, but not sure about any wider.
> ...


If you're using open stringers and insetting them 4" on either side, you could use 3' tread and only have an open span of 28".


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## Arky217 (Aug 18, 2010)

Well, one reason for asking is that the box stores have the stringers and treads precut, and the treads are 2x12's available in 3' and 4' widths.

The stringers are a real deal; about the same price as if you bought a regular treated 2x12x8'.

And the treads, although about twice that of buying the 2x12's alone, have the fronts rounded, have grooves for traction, and most important, both the stringers and treads are treated after they are cut, and with a higher concentration than a regular treated 2x12.

If I go with the 4' treads, I wonder how far I should inset the stringers to minimize bounce.

Thanks,
Arky


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## gregzoll (Dec 25, 2006)

I would. You never know how much someone weighs going up those stairs, or you have to take something really heavy up that way. I would go with 3 stringers for a 4 foot, just to be safe.


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## Gary in WA (Mar 11, 2009)

Species of wood, open vs. closed stringers (one spans double the other), tread thickness, etc., figs. #28, 29 and Table 6: 
http://www.awc.org/Publications/DCA/DCA6/DCA6-09.pdf Details of bearing post required for handrail......

Gary


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## Ron6519 (Mar 28, 2007)

Arky217 said:


> Well, one reason for asking is that the box stores have the stringers and treads precut, and the treads are 2x12's available in 3' and 4' widths.
> Arky


Pre cut stringers only work if the height is set up for it.


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## carpitect (Jun 15, 2011)

The stringers are like floor joists, 16"-18" should be the maximum spacing. If you opt for the 36" treads, use 3 stringers - 18" on center. If you go for the 48" treads, go with 4 stringers - 16" on center. I would minimize any overhang - you need something to connect the railing to. 

Spend the extra money now, do it right, and you won't have to spend extra money to fix it later.


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## 12penny (Nov 21, 2008)

Ron6519 said:


> Pre cut stringers only work if the height is set up for it.


 
Agreed...unless taken into account in the planning stage or you get very lucky. Funny though...lots of people buy them. 

To answer the question, I would'nt feel confident with 2 stringers supporting a 36" wide stair. Spend another $20 and do it right.


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