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RE: Question for East Coast Engineers[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaoc(--nospam--at)seaoc.org>
- Subject: RE: Question for East Coast Engineers
- From: "Dennis S. Wish" <wish(--nospam--at)cwia.com>
- Date: Sat, 9 May 1998 11:21:01 -0700
Robert, many good responses in your post. You confirmed what I originally thought was the intent of Conventional Framing for post WWII FHA Homes. You also hit on a very important observation that can account for most of the problems that arise with Conventional Construction. 1. I agree that the quality of construction has deteriorated since the early seventies. However, I don't believe that this has anything to do with available materials or proprietary connectors. I believe it has more to do with labor cost and the tradeoff of using unskilled, lower cost labor to accomplish the same work in a much shorter period of time. 2. It's not necessarily that labor has gotten worse (although I feel that this is a large part of the problem) but rather the complexity of the allowable design has gotten much more complicated from the post WWII FHA 900 S.F. square box similar to what we see in the Silver Lake region of Los Angeles. 3. Framing used to be an artform which is no longer profitable today. This leads to the new Framer that does not posses the skills of the "old-timers" who knew how to assemble wood structures. We can not expect to increase the skills of the present day framer unless we require him to prove his/her competency and understanding of the provisions of the code. The dichotomy is that the lobby against additional education and testing of Contractors is stronger than the lobby to tighten their requirements. Any individual who can wield a hammer can call himself a framer and work under a GC's license as an employee. Typically, the GC is running more than one project at a time and relies upon the framers historic references to accomplish the project. I think you can see from many responses (and from the forthcoming web pages devoted to these quality problems) that we have a real problem in this area. 4. The intent of the code has or is changing. Prior to the '91 code we were not concerned about mitigation of damage. With the insurance companies backing out of high risk area's like California, the home owner is left unprotected and financially liable for any damage that occurs. With contractors liability expiring after ten years, there may be no recourse for poor construction quality unless it can be proven that it was due to criminal neglect - something I have yet to see proven in court. Finally, with the knowledge that you admit exists, there would be no excuse to allow compliance to a prescriptive measure that is incomplete. This includes the connection of interior shearwalls (as you pointed out) as well as the selection of headers based upon maximum truss spans of 34-40 feet. There are many loopholes - even in the IBC. I complimented the IBC because it is an improvement in this section of the code. However, we are not doing the homebuyer justice to produce only a half attempt at a prescriptive measure that leaves a great deal to interpretation. Until the "Framer" can be required to be licensed in his particular trade and prove competency in the sections of the code that deal with the materials he chooses to qualify for, we must provide 100% prescriptive methodology or none at all. This does not mean I want to abolish conventional framing, this means that I want to provide a complete prescriptive measure to assure construction quality or to weed out the "bottom feeders" we frequently draw attention to. I have sent my comments to the SEAOSC committee that works with wood provisions for the IBC. I have no idea whether it was received, reviewed or considered more than an intrusion from the outside. Those reading this who have some responsibility to this section of the IBC need to respond to this list so that we know that the many issues raised are being considered by SEAOC. It would be great to have SEAOC take a position on this section of the code and reaffirm their position to those members of this list for a start. Thanks for your comments, they went a long way to clarify the intentions of the Conventional framing. I think it boils down to one comment you made that shows the problems we face: " The issue of no requirement of connecting interior braced wall lines to the roof diaphragm was an initial oversight that was to be corrected by a further code change but ICBO suspended code development for the UBC before the change could be processed." If this is not corrected at the present, there will be thousands of SFR that may be constructed with this deficiency. Sincerely, Dennis S. Wish PE -----Original Message----- From: Robert J Bossi [mailto:rjbossi(--nospam--at)sonic.net] Sent: Saturday, May 09, 1998 9:51 AM To: seaoc(--nospam--at)seaoc.org Subject: Re: Question for East Coast Engineers Richard_Ranous/OES(--nospam--at)oes.ca.gov wrote: > Maybe Kelly Cobeen or Bob Bossi can provide us an > update? The conventional construction provisions of the 1994 and 1997 UBC are substantially different than the 1991 edition. Until 1994 the only limitation was "unusual size and shape", terms that were undefined. Kelly Cobeen, Ed Zacher and I were members of the Conventional Construction Task Force that developed the current provisions. That task force included designers, contractors, the wood industry and building officials. The purpose of this effort was two fold: 1. to provide uniformity in the application of the conventional construction provisions; and 2. to address the changes in architecture that occurred since the post W.W.II FHA "tract box" style of house had given way to more complex "modern" architecture. The code change did several things. It limited the use of conventional construction to only certain occupancies and certain maximum load limits. Prior to 1994 there were no such limits. It also defined what "unusual shape" meant using code defined irregularities. Unusual shape became moot once maximum braced wall line spacing was developed. Very little changed in the actual provisions except for a few connection nailing improvements. For further detail see the September-October 1996 Edition of Building Standards Magazine. The issue of no requirement of connecting interior braced wall lines to the roof diaphragm was an initial oversight that was to be corrected by a further code change but ICBO suspended code development for the UBC before the change could be processed . Overall I believe that the current UBC (and future NEHRP and IBC) conventional construction provisions are a significant improvement over those before 1994. Regardless of what calculations might show, well built and maintained conventionally constructed buildings even from the early 1900's, before codes, performed well as long as cripple walls were braced and the building was anchored to the foundation. Remember also that prior to the 1970's few, if any, wood frame buildings were "engineered". My experience in evaluating "failures" is that they can much more appropriately be attributed to poor construction practices and deterioration than the design methodology used. In fact, I found after the Loma Prieta earthquake that newer engineered structures often performed worse than older undersigned structures of the same type. I believe that this was primarily because the engineered structures used fewer, stronger (but not necessarily stiffer) and more highly loaded lateral force resisting elements. Many of these elements were plywood behind stucco and were found to be totally deteriorated due to moisture infiltration and decay. The question of the need to "engineer" all buildings cannot be addressed by the code. In California it is the Engineer's (and Architect's) Act that governs (Cal B&P Code 6737.1). Any residential wood frame building of four or less units that conforms to the conventional construction provisions is exempt from professional design and, even then, only those elements that deviate from the conventional construction provisions need be "engineered". It would take an act of the state legislature to change that and I think we can all predict the outcome of such a bill. If any one feels that the IBC conventional construction provisions need further change, there is still time to submit challenges to the next (final?) draft of the 2000 IBC.
- Re: Question for East Coast Engineers
- From: Robert J Bossi
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