On Thu, 16 Feb 2006 17:30:55 -0500, Goedjn wrote:

On 15 Feb 2006 12:59:08 -0800, wrote:

We recently purchased a house in (earthquake prone) Southern
California. The property is surrounded by a 6' cinder block wall,
built around the same time the house was (1965). It has become apparent
to me that the wall was constructed without rebar or concrete
reinforcement and, in a few places a couple courses of block have
fallen off. My question is if it is possible to retro-fit the wall to
make it secure. In other words, can the decorative course of brick at
the top be removed, rebar and concrete added to stabilize the wall or,
should the whole thing be removed and rebuilt?


Is your objective to prevent quake-damage to the wall, or
just to keep it from falling on anyone when it is damaged?
If its regualr concrete-masonry units, then yes, you
can saw (or bash) the top row off and insert vertical rod,
which should keep it from spitting out individual blocks
on peoples heads. If the wall is actually necessary
because of the people-environment, this would be a good
time to retro-fit the wiring for an intrusion-detection
systems. Another alternative would be to cover
one or both faces with hardware cloth and parge it,
which would also prevent it from spitting out individual
chunks of masonry. I can't think of anything short
of buttresses that would keep the whole thing from
coming down all together in a major quake, but I'm
not an expert.

To keep it quake proof, he must drive 10 inch steel well casings down
to the core of the earth, and place them every six feet along the
wall. Then these casings must be filled with concrete and welded
together about 2 feet below the surface of the ground, with sleeves
that allow for flexation during a quake. Attached to these casings
and the welded frame must be thick rubber shock mounts between the
casings and a heavy steel welded frame. Inside each frame the blocks
are placed with rebar in each course. This should make a wall that
will remain stable during a quake, but may cost several hundred
million dollars to construct.

The other solution is a picket fence. The worst thing that can happen
to a picket fence during a quake is a few boards falling off, or a
section landing on someone's toes.