[Greenbuilding] Earthquakes and older houses
Bob Waldrop
bwaldrop1952 at att.net
Wed Mar 30 14:52:56 CDT 2016
Thanks everyone for these detailed comments and suggestions. There's a
lot to take in, I'm printing the emails and will share them around a bit
and see about coming up with a plan of action. One "low hanging fruit"
item we're taking care of this week is making sure that nothing
furnishing-like can fall on us while in bed or casually sitting around.
This involves re-siting some large mirrors, paintings, and book cases.
Bob Waldrop, Okie City
On 3/30/2016 8:32 AM, Alan Abrams wrote:
> Bob--
>
> imagining the Oklahoma version of "The Big One," I think the gravest
> danger is the collapse of the brick foundation walls. in our
> region,bricks from the 20's can be pretty soft, and the mortar can be
> powdery.
>
> if that all describes the scenario, simply anchoring the floor system
> to the top of the brick walls might be inadequate. the strength of the
> foundation walls would be limited to the compressive force exerted by
> the weight of the house above. in this sense, the weight of the brick
> veneer is your friend--but I think the veneer is going to be the first
> element to fail when things start to shake. The point being, that even
> if the floor is anchored, the foundation walls could rotate in,
> between corners.
>
> one could of course jack up the house and install a new reinforced cmu
> or poured concrete foundation beneath it. Or form up and pour new
> walls against the existing walls.
>
> but less intrusively, one might strengthen the walls by increasing the
> compressive force--perhaps by excavating and installing a set of pier
> footings at intervals around the basement perimeter, each pier footing
> undermining the existing footing--maybe 2' wide or so. each pier would
> have a reinforced anchor bolt, to fasten some set of threaded rods and
> turnbuckles--which in turn would be bolted to the floor joists.
> Ideally, there would be two rods for each pier footing, run diagonally
> in opposite directions, parallel to the foundation walls.
>
> There a lot of boggling variables here--such as the moisture content
> and plasticity of the soil, height of backfill, direction of seismic
> waves--so sizing the footings and rods, and determining how many to
> install would be speculative. Maybe a big shaker would overcome this
> effort. Or maybe it would hold up long enough for you to escape before
> it all comes down. I don't envy your situation.
>
> -aa
>
>
>
> Alan Abrams*
> */certified professional building designer, AIBD
> certified passive house consultant, PHIUS/
> /certified passive house builder, PHIUS//
> /cell 202-437-8583
> alan at abramsdesignbuild.com <mailto:alan at abramsdesignbuild.com>
> HELICON WORKS /Architecture and Education/
> <http://www.heliconworks.com/index2.html>
>
> On Tue, Mar 29, 2016 at 11:05 PM, ErgoDesk <ergodesk at gmail.com
> <mailto:ergodesk at gmail.com>> wrote:
>
> California... I would reinforce your FIRE Insurance first.
>
> Sincerely,
> George Hawirko_
> _
> _http://about.me/StyroHome_
>
>
> On Tue, Mar 29, 2016 at 11:40 AM, Jason Holstine
> <jason at amicusgreen.com <mailto:jason at amicusgreen.com>> wrote:
>
>
> I think you can find retrofit resources online from
> California. I think their state emergency mgmt agency, state
> NAHB, etc. have docs. It could become a nice side biz
> tightening up Okie corrals.
>
>
>
> On 3/29/16 1:41 PM, "Bob Waldrop" <bwaldrop1952 at att.net
> <http://bwaldrop1952@att.net>> wrote:
>
> > So here in central Oklahoma, we have been experiencing a growing series
> > of earthquakes over the last few years. The USGS just
> released a map
> > showing the risk of human-induced earthquakes, and Okie City
> is right
> > there. The news said we were at perhaps a 10% risk of a level 6
> > earthquake. Most of the thus far have been in the 2 to 4 range.
> >
> > Now we are not only tornado alley, but also earthquake
> central, more
> > earthquakes last year even than California had.
> >
> > I lived in the Bay Area of California and in SLC (on top of
> the actual
> > wasatch fault a geologist friend told me), and never
> experienced a
> > quake, but I've felt several here. I've also been watching
> the cracks
> > in the interior plaster/lathe walls and my exterior brick
> veneer develop
> > and progress.
> >
> > I do have earthquake insurance, but it is really only good
> for a
> > complete catastrophe. It has a 10% deductible, and it
> doesn't cover
> > masonry.
> >
> > The house has always seemed very sturdy. It was built in
> 1929, the
> > studs are on 12 to 14 inch centers and are a hard wood. THe
> sheathing
> > is 1 x 8 planks. Then there is brick veneer over that. The
> foundation
> > is brick. The back and front porch construction seems
> separate from the
> > rest of the house. The concrete front porch is certainly
> pulling away
> > from the rest of the house over the 16 years I've lived here.
> >
> > Any thoughts about retrofits that would strengthen the house
> in the face
> > of the growing earthquake risk here?
> >
> > Bob Waldrop, Okie and Shaky City
> >
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