So far as I know, NFPA has dictated the 7"/11" riser/tread ratio. IMO,
it's not as comfortable as the 7 1/2"/10 1/2" ratio, but it's the *law* in
Florida and Louisiana.
In 1993, in an industrial plant in Louisiana, the plan reviewer would not
approve the 7 1/2"/10 1/2" ratio. In the process, I *discovered* that
Florida had incorporated the NFPA requirements by reference. BTW, the 1993
OSHA still accepted the 7 1/2"/10 1/2" ratio. The local building official
was *not* impressed.
It's a *terrible* waster of space, because it costs an extra riser/tread in
each flight of stairs. Using a 7" maximum riser, a stair with a 12 foot
rise will have 21 risers (20 treads). Compared to the same stair with a 7
1/2" maximum riser, there will be 20 risers (19 treads). At first glance,
this doesn't seem like a big deal, but the run of that stair will be 20
1/2" longer with the 7"/11" ratio.
This *minor* detail can cost extra landings (and some *nasty* structural
details) when fitting stairs within a restricted area.
So far as I can determine, this decision is not dictated by safety, but
someone's personal prejudice.
I'm glad I'm getting old. I am becoming weary of political solutions to
Fountain E. Conner, P.E.
1724 Beaver Pond Rd.
Gulf Breeze, Fl. 32561
> From: KSP <lvtakp(--nospam--at)yahoo.com>
> To: seaint(--nospam--at)seaint.org
> Subject: BOCA stairs
> Date: Thursday, April 27, 2000 6:56 AM
> This isn't really a structural question but I'm sure a
> lot of you have experienced this situation. We do a
> lot of industrial work and are often bound by BOCA.
> It seems to me that we must design our stairs with a
> 7" max riser and an 11" min tread per BOCA but it
> doesn't seem to me that many other architects or
> engineers are doing this for industrial applications.
> Am I missing something in the Code that allows me to
> not have a stair going up to a piece of equipment that
> has such a shallow slope that my grandmother can climb
> up it? (I know about the alternating tread stair but
> that is not what I want.)
> The other thing that doesn't seem to be done by most
> other engineers in industrial buildings is the
> handrail extensions at the top and bottom of the
> stairs. It seems to me that they would be required at
> all stairs here in BOCA land.
> As always - thanks for your insights
> Ken Peoples, P. E.
> Lehigh Valley Technical Associates