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More Stringent Seismic Zone

joetheinspector

Registered User
Joined
Jan 1, 2010
Messages
150
We are under the 2009 IRC and IBC

Does the Building Official have the authority to designate a higher seismic design category? If so what code or law allows that authority? Does it need to be done by ordinance?

On the Map in the IRC our municipality is in a seismic design category C.

However there has been local testing by seismic experts that shows that we should be in a design category D. There are official reports with the studies.
 

Mark K

Platinum Member
Joined
May 12, 2010
Messages
1,664
Building code regulations are laws and any laws can not be imposed on individuals unless they have been properly adopted by the appropriate legislative body. The Building official may make recommendations to the legislative body but cannot act on his own. Was the building code adopted by the state or by the local jurisdiction?
 

mark handler

Sawhorse
Joined
Oct 25, 2009
Messages
10,784
Location
So. CA
International Residential Code 2009

SECTION R301 DESIGN CRITERIA

The jurisdiction shall fill in this part of the table with the seismic design category determined from Section R301.2.2.1.

R301.2.2.1 Determination of seismic design category. Buildings shall be assigned a seismic design category in accordance with Figure R301.2(2).

There is a similar section in the IBC
 

joetheinspector

Registered User
Joined
Jan 1, 2010
Messages
150
The local municipality has adopted the State Building Code. The State has adopted the 2015 IBC and IRC with amendments. The seismic section of the code has not been amended so the IRC or IBC is what has been adopted. So if we go more stringent it must be done by ordinance? Is this correct? Doe everyone agree with Mark K?
 

Mark K

Platinum Member
Joined
May 12, 2010
Messages
1,664
You state that the municipality has adopted the State Building Code. Did the local municipality have the option of not adopting the state code? What does the state say about what sort of changes to the state code the local municipality can adopt?
 

tmurray

Registered User
Joined
Jun 10, 2011
Messages
1,882
Location
NB, Canada
Mark K just hit the nail on the head; unless there is legislation that allows municipalities to modify the state adopted code, any modifications may be deemed unenforceable. Typically lower governments cannot modify laws adopted by higher levels of government unless stated in the law.
 

joetheinspector

Registered User
Joined
Jan 1, 2010
Messages
150
Here municipalities can have local amendments that are more stringent than the State code. Municipalities can not have amendments that are less stringent than State code
 

Fort

Silver Member
Joined
Jan 12, 2012
Messages
128
Location
California
Municipalities can not have amendments that are less stringent than State code
While this is technically true, there is also the option that a more detailed and site specific seismic analysis may be performed for an area that actually result in lower seismic design values than those provided by the USGS maps. The AHJ may approve the results of such a report for use in the design of a structure.

It would seem that they have allowed something that is less stringent than code, but actually it is an approval of lower values based on more site specific geotechnical analysis.
 
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