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.
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.
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undefined terms "unusual size and shape" have been replaced by detailed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 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
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.
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).
Contractor's State License Board is also in the process of developing a
"merit badge" system.
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?
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.
can always add to the code to make construction more expensive but only
at significant social costs.
Bob Bossi, PE
Conventional Construction Task Force