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Re: Questions about Residential design and 1997 UBC

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Dennis S. Wish PE wrote:

4. Prescriptive Residential Construction Vs New Design Standards -I feel that there are a few potential problems: A) Conventionally framed homes will not calculate (by the number - especially if a raised floor is considered) to be of equal or greater strength than engineered products. No provisions are made in the '97 code to strengthen Conventional Framing OR to revise the code to correct mistakes and missing information in the publication. A loophole in the code exists that will allow Conventional Framed homes to be at greater risk AND unethical developers will take advantage of the ommissions of the code to increase profits on these homes while marketing them as equivalent complying products.

It is true that conventionally framed buildings won't "calculate".  So what.  It is how they perform that counts.  Conventional construction has a long history of satisfactory performance in earthquakes.  Yes, there have been failures of older buildings with unbraced cripple walls but we have retrofit standards to correct this.  There is no loophole in the code.  Conventional construction was included in the code by the same methods as any other provision.  Developers are not unethical to use it.  I have never seen any developer market a new residence based on its seismic resistance.  The purpose of the building code is the protection of the health and safety of the general public, not the protection of individuals from property damage or economic loss.
 B) As the definition of Conventional Framing increases to allow larger and more irregularly shaped structures (not load path irregularities) more architects and builders will attempt to make larger scale custom homes conform to conventional framing standards. This would be counter-productive to the intent of the new code provisions if the presecriptive measure does not correct ommissions.

The definition of conventional framing has not increased.  As of the 1994 UBC, the undefined terms "unusual size and shape" have been replaced by detailed limits on occupancy, dead load, room size (braced line spacing) and degree of irregularity.  Additional connection have been required.  As a result, far fewer building will be able to qualify for the use of conventional construction.
 C) Conventional Framing does not require Structural Observation provisons which has historically identified problems in the construction phase and helped to improve quality of construction subsequent to Northridge and Hurricane Andrew.

Structural Observation should not be necessary for conventionally framed buildings. An AB 717 qualified (ICBO certified) local building inspector should be able to make all necessary inspections.
 D) There are no present provisions which requires continuous education and training for for framers (although the Wood Truss Council of America has been backing a framer certification program which is also, as I understand it, supported by NAHB).

The California Contractor's State License Board is also in the process of developing a "merit badge" system.
 Are we putting the cart  before the horse by creating more regulations to prevent construction quality control problems rather than attempting to educate the construction industry on interpretation and understanding of the conventional framing section of the code?

Where are "we" creating more regulations that discourage quality control?
 Will the greater restrictions posed by the '97 UBC cause developers and Architects (designers) to seek closer compliance to conventional framing which will produce a product designed to a lessor standard than we presently have in the '94 code?

It is unlikely because the more restrictive conventional construction provisions will not allow this to happen.  Ther is however the partially ebgineered, partially conventional structures.  This, howver, is not something the building code can fix as it would require, in California at least, a change to both the engineer's and architect's acts.

With this said, I still believe that there is room for improvement in the conventional construction provisisions of the UBC, IBC and NEHRP but I also belong to the Frank, "where are the bodies", Lew school.  Take a look at all the conventionally framed buildings that have ever perfrormed so poorly as to cause death or serious injury to their occupants and ask yourself would this of occured had they been constructed to conform to the current codes conventional construction provisions.  To the extent that the answer is no, the cuurrent provisions are adequate.  If you identify any areas where the answer is yes, then that is where the code need to be changed.   Anything else is regulation for regulation sake.

Remember, we can always add to the code to make construction more expensive but only at significant social costs.

Bob Bossi, PE
Past Chair, Conventional Construction Task Force