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Re: ground snow v. roof snow - which is it?

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Scott,
Do you not have a right to appeal?  In Ontario, if we
feel an official has erred, we can appeal to the Ont.
Building Code Commission for an interpretation or ruling.
Gary


On 21 Sep 2005 at 12:24, Scott Maxwell wrote:

> I don't disagree with you, but you have to realize that not all states
> adopt the codes for required statewide use.  In some states, codes are
> adopted (and potentially modified/added to) by local jurisdictions
> (counties, cities, etc).  That _WAS_ the case in Michigan until
> recently. It was not until a handful of years ago that Michigan went
> to adopting a code (which they DO modify some), the IBC and IRC, for
> state wide use. It used to be that each local jurisdiction would adopt
> what they wanted. Lansing, MI had adopted a version of the UBC.  Most
> jurisdictions in the SE Michigan area adopted a version of the BOCA,
> but one city might use 1993 while another used 1996, etc.
> 
> And the point is that the jurisdiction (state, city, county, etc) that
> legally adopts the codes can modify it as they see fit...and most do
> so.
> 
> And beyond that, even in some states where there is a state-wide code
> adopted, it is a "minimum" code.  In otherwords, local jurisdictions
> (cities and/or counties) can still modify the state code _IF_ they
> make it more conservative (and requiring the use of full ground snow
> load rather than roof snow loads per ASCE 7 is more conservative).
> 
> And like it or not, by and large the local code official is the
> "interpreter' of the code.  While it is certainly possible that they
> could interpret it wrong, it becomes a hassle (at minimum) to argue
> against such misinterpretations at times, to (at the extreme) bad
> thing for the well being of your project (the good old phrase of "I
> fought the law and the law won" comes to mind).
> 
> Scott
> Adrian, MI
> 
> 
> On Wed, 21 Sep 2005, Jordan Truesdell, PE wrote:
> 
> > I believe that the requirement to use ground snow would have to be
> > proposed and included in the legislation adopting the code, or in
> > subsequent published addenda.  Code officials, as far as I know, do
> > not have the right to change the building code, though some feel
> > that they do. That's the whole idea behind using model codes.
> > Otherwise, we're back to pre-national code times when every
> > jurisdiction makes it own rules. It may not be worth the fight - its
> > not our money we're spending by upsizing roof structures - but the
> > courts would likely side with the letter of the law, and in this
> > case the building code is extremely clear. "Shall be determined in
> > accordance with" doesn't leave much wiggle room.
> >
> > Jordan
> >
> > Scott Maxwell wrote:
> >
> >  Jordan,
> >
> > Not so quick.
> >
> > You have a point, but then Jim does as well as local code officials
> > or states can "modify" the plain vanilla IBC (i.e. adopt it with
> > modifications/additions).  From my experience, some local
> > juridictions will require the use of the full ground snow load as
> > the roof snow load (i.e. no modifications to flat roof snow load or
> > sloped roof snow load). Now, it is my belief that this is largely
> > due to the IRC (which I believe REQUIRES the use of ground snow load
> > and does not PERMIT modifications per ASCE 7) and local code
> > officials not realizing that such it not "required" if the design is
> > an engineered design (i.e. IBC is used rather than IRC).
> >
> > Scott
> > Adrian, MI
> >
> >
> > On Wed, 21 Sep 2005, Jordan Truesdell, PE wrote:
> >
> >
> >
> >  Jim, I think you've got is bass ackwards ;-)
> >
> > I quote, "Design snow loads shall be determined in accordance with
> > Section 7 of ASCE 7..." This is the first sentence of section 1608
> > of the 2000 IBC (Snow Loads).  The ellipses referes to the
> > requirement that the roof load must not be less than the roof live
> > loads specified in the Live Load section, 1607.
> >
> > That's pretty cut and dried - engineers (actually, anybody) are
> > specifically allowed by the code to use any and all reduction (or
> > amplification factors) they deem appropriate, as listed in ASCE 7. 
> > The code writers appear to have specifically allowed the reduction
> > of loads where allowed by the ASCE.
> >
> > As has been mentioned, the span tables are probably based on ground
> > snow loads, and should not be altered without analysis by a
> > registered engineer.  Ground loads are convenient, because that's
> > what's in the table.  I would suspect that the tables also assume
> > partial exposure, ventilated roof over thermally isolated living
> > area, Terrain Categories A, B or C, an importance factor of 1.0, and
> > no drifting conditions or sliding surcharges, and - of course - no
> > unbalanced loads.  Prescriptive design has its place, but can always
> > be overridden by proper analytical techniques. (That doesn't always
> > mean reduced loads, btw)
> >
> > Jordan
> >
> > Jim Wilson wrote:
> >
> >
> >
> >  It seems as if the code writers have eliminated the
> > option of reducing snow load when using prescriptive
> > design.  Subsequently, it is up to the local enforcers
> > to decide if an engineered design is permitted to
> > include the reduction factors.  Does that sound
> > correct?
> >
> > Jim
> >
> >
> >
> >
> >
> >
> >
> >
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