Given the tight radius of the inside of the spiral, you would need 1/4" or
maybe 3/8" plywood to make the assembly the architect speaks of.
I'd like to see photos of a completed assembly constructed using this
method.
Cutting this glued and screwed assembly on a diagonal seems a little suspect
to me.
Its not like a standard "glu-lam" spiral star stringer:
http://www.arcways.com/detailspiral.asp?SUID=33
However, I used "the google" and "the internets" and found this:
http://www.eng-tips.com/viewthread.cfm?qid=163186&page=5
Cheers,
David L. Fisher SE PE
Senior Director
The Fisher Companies Ltd. - Cayman
372 West Ontario Chicago 60610
75 Fort Street Georgetown Grand Cayman BWI
319 A Street Boston 02210
312.573.1701
312.573.1726 facsimile
312.622.0409 mobile
www.thefishercompanies.com
www.fpse.com
"England expects every officer and man to do his duty this day."
- Admiral Horatio Nelson
HMS Victory
Trafalgar 1805
-----Original Message-----
From: Michel Blangy [mailto:mblangy@satco-inc.com]
Sent: Tuesday, September 02, 2008 1:57 PM
To: Seaint@Seaint. Org
Subject: Site Built Spiral Stair Case
An Architect wants to use a method I've never seen before to construct site
built spiral stair cases. We do a lot of tight radius spiral staircases here
in southern California residences. Typically, the outer and inner supports
of the treads are continuously supported by tightly spaced studs. The idea
now is to line the inside face of the spiral with multiple layers of
plywood, glued and screwed in place and then, after the glue has had time to
cure, the plywood and interior support studs are to be cut parallel to the
tread nose line at some depth creating a spiraling plywood beam. I have no
clue as to how to calc this out, but the architect has seen several
constructed and swears they are quite solid. How might one spec a load test
for such a thing and does this test indemnify the EOR? What other concerns
if any would you have?
Thanks in advance,
Michel
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