Does anyone know of a design source for stringer spans, like the span tables in code books for rafters and joists?
I ask because it’s occurred to me that I’ll span the same distance or more with a pair of housed 5/4 x 10 stringers as I will with three notched 2×12 stringers. I know why, and have confidence in my design, but realize that it’s all intuitive and that intuitive design has limits.
Thanks for any help.
Andy
“Never try to teach a pig to sing. It wastes your time and annoys the pig.” Robert A. Heinlein
“Get off your dead
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"Stair Builders Handbook"????
Avail here
http://www.amazon.com/gp/product/0910460078/002-7408363-5309639?v=glance&n=283155
Thanks, I don't have that one. I'm ordering it, but have my doubts. I've never seen this sort of table published, but there must be design values somewhere.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Yeah...got me wondering too. Even checked Architectural Graphic Standards...."the bible"..... no charts or calcs for stringers at all.
HMMMMMMMM.
Hey Andy: your question is something that has been nagging at me for a while as well. So I dug (and dug and dug) and surprisingly, have come up with very little.
The best I could do is that for a standard stringer, the accepted practice is 2x12 18" OC. No discussion of how deep the treads/risers might cut it, or if it's a very high ceiling, it's overall span limitations.
I dug out an old engineering book which likewise had no coverage of stringers except a very brief explanation of using the effective depth of the stringer (perpendicular to its length) at the cuts. Again, not a high level of confidence because there was no warning about grading the 2x12 stock to make sure the meat left was at least as good as what was cut.
For housed stairs, nothing, nada, ziltch.
If someone can come up with more, I'd also be very interested.
"A job well done is its own reward. Now would you prefer to make the final payment by cash, check or Master Card?"
Intuitively, and because of the wood available today, I cut all my stringers from LVL stock.
I have a set of Audel's Carpentry books (ca. 1912) that, IIRC, do have some stringer specs. But I'd really have to do some digging to locate those books.....and I'm not in the mood. Sorry! :-)
I am sure it is in one of the books I got from apprentice school. If I can find the book I will look for you and post something else. Off to see what I can find, I like a challenge.An inch too short. That's the story of my life !
bstcrpntr --- I hope to grow into this name.
Personally, I compare stair stringers to floor joist charts. By using the thinest portion of the stringer as the thickness, and the horizontal run for the length it's pretty easy to see how the design compares to floor loads.
Having said that, there's a lot of interpretation and adjusting, but it does seem to give some good information. The charts show L/360 deflection with 2x6 #2 doug fir (2x12 with cuts), 12" oc (3' wide with 3 stringers), as being good to about 10'6". That seems intuitively correct if there aren't midspan supports. Today the architect and I were working out some loads with 5-1/2" x 1-3/4" LVLs, but I forgot to get the numbers off his chart to compare with normal dimentional lumber.
Good stairing!
Thanks all for the input. If anyone comes up with anything, please post it. As some of you know, I'm working on a book on stairbuilding and would love to include this info.
The idea of using joist span tables sounds OK except for two things. Whenever you rip, or I'd say notch, a graded piece of lumber, it loses its grade. For example, if you rip a 2x10 to 7 1/2 in., it's not rated as a 2x8. That's because the lumber grader looks at the location of the board's defects, and a knot at the edge of the board weakens it far more than a knot in the board's center. The other factor works in the stairbuilder's favor. That is the way that risers act as beams at each step, effectively spreading the load out over all the stringers.
It's complicated. Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
You might try contacting the US Forest Products Lab in Madison.I think that is the main one, but I don't know if they are the ones that do the structural testing or not. But they should be able to give you a direction.And there are a number of Universities with engineering/building science/foresting departments that some one should have this or maybe make it a class project.Here is on good guy to contact. I forget his name, but he is in Virgina (and I think retired from a University) and has written the different articles on deck ledger attachments and deck rails attachments. I think that they where in JLC, but might have been in FHB. It might be Frank Worscete or something like that.
That's a good idea. That engineer who did the railing attachment article in JLC certainly took a conservative approach.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
TrusJoist MacMillan is marketing some sized of their LSL (laminated strand lumber) as stringer stock.
Their LSL is also used in rimboard and structural beam and column products.
Go to their site, find the brochure, and download it. They show allowable spans for various sizes, and my guess is that those spans are similar to sawn lumber of comparable size.
Will do, Gene. Good lead.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom