I agree regarding the properties of stucco and drywall.
However, here are my reasons not to use stucco/drywall shear walls.
Nowadays, the homeowners (and their lawyers) want the damaged
walls to be restored "exactly as they were." They object to any
attempt to repair the stucco (although, as we know, the crack repaired with
construction adhesive is stronger than the surrounding intact stucco...).
So, it is much easier for everybody (including contractors) just to
"shear" everything with plywood as it was recently discussed on this
list. In this case, there cannot be any objections to
stucco and drywall repairs.
The important part of all of it is that the currently existing
earthquake insurance is, eh, not quite what it seems to be. At 15%
deductible, the homeowner is pretty much on his own with
This earthquake was really weird, and IMO could damage even
adequately designed/built structures. I saw a house that did the
Jumped up as a whole (strange for a very large, but flimsy
one-story structure, even without anchorage to footings);
The perimeter footings spread out along one
The house came down, landing inside the perimeter footings
(not quite missing them, though);
About 30-to-50% of interior piers (obviously, not even
nailed to baseplates and floor beams) were dislocated or missed during the
The soil around the house shifted about 1.5 inches and
The stone chimney shifted 1.5" - as a
Other than that - the house was amazingly
(The house was on sand, with water table about 12" below
I did not see anything like that after Landers, Northridge,
and Hector Mine earthquakes...
Steve Gordin SE
----- Original Message -----
Sent: Monday, December 29, 2003 2:28
Subject: Re: Paso Robles and other
Thanks for the report even it you didn't say what
their religion was. ( sorry but I was beginning to think this
list had changed to a philosophical discussion medium).
Seriously, I would not give up on stucco and
drywall completely. They are good products if designed and installed
properly. Was the stucco attached to "self furring" lath? And was
it nailed (through the drip screed where staples will not penetrate) to
the sill plate? Also, did the design take into account the torsional
deformations at the plan irregularities and where the second floor terminated
at a two level high ceiling section? I have seen our building code
changed in the past to increase demand and prohibit materials when what
is needed is better design and structural observation (without having to get
permission from the architect), all of which require that engineers not only
learn what to do but also require higher fees to perform the
detailing and observation necessary.
----- Original Message -----
Sent: Monday, December 29, 2003 11:52
Subject: Paso Robles and other
The original message was too long, so I divided
it in two, and removed the attachment...
Part I: Happy
I just came from the Paso Robles Area where I was
inspecting damage after the recent earthquake. Here are some
observations from the site.
Several newer - and quite expensive - houses
sustained substantial cosmetic and even some structural damage which I
would not expect from such structures. Generally it proved to me
that drywall and stucco shear walls should not be used - especially in
irregular houses - no matter how low the calculated forces/stresses
I also observed distinctive soil damage that I did not
see a lot during Northridge. In one instance, a
three-car garage, separated from the main house by a breezeway, visibly
settled more than 1 inch (without any substantial damage/distortions
inside it!). The garage was obviously built on fill while the
house proper had a sub-grade level with retaining walls. Strangely,
the house is about 15 years old, and never had settlement problems (no
noteworthy old cracks in stucco).
The other case was even more amazing - a 3000 sq. ft
one-story house on a flat lot on top of a hill (as many of them are in
that beautiful country, imagine the view). The house sustained very
little - barely any - damage to the superstructure, in spite of heavy tile
roof, brittle finishes, and irregular shape/composition. But the
slab it was built on cracked intensively - long linear cracks in, and under,
ceramic floor tiles. Some of the cracks have vertical offsets up
There was some evidence of topsoil fissuring
and distortion/shifting of the underground pipes; a large
swimming pool had drained since the earthquake (in 7 days).
It looks as if the apparent underlying rock-like
shale was shifting along its weak planes... Can it happen that
way? And if so, why so little damage to the
To illustrate the force of that earthquake: a crew-cab
F150 was parked in the garage (naturally, a 10-car garage). The
sectional door is now bent and would not open - apparently, because the
truck was slammed against it from inside, and then was pushed back (~36"
amplitude movement). All that is verifiable by clearly visible
tire marks on the garage floor.
Also, it was nice to see the tower in the downtown Paso
Robles already replaced with a wood-framed OCB-sheathed one. BTW, a
very neat job, and, obviously, much safer structure (attached)... I
presume it is the one that collapsed and was in all news.
Other than that -
Happy, Healthy, Peaceful,
and Prosperous New year to all.
Steve Gordin, SE