[Strawbale] Welded wire mesh in Lime plaster

[Leanne Rellstab]

If I understand you properly, Doug, you're putting little band-aids around,
extending eight inches into the plaster from wood (posts and plates). This
would serve to nominally tie the wooden structure to the plaster, and reduce
cracking at wood/plaster joints but does nothing to increase the strength of
the walls themselves.  A much better tie would be achieved using expanded
metal lath, since 8" of WWM doesn't have much for plaster to adhere/grab. To
achieve the strengths of the California test, one would need to have mesh
very securely attached (minimum each wire joint, 2" oc) on all four sides of
the wall.

I should reread the tests, if memory serves they just used the welded wire 
into the plaster. I don't remember seeing that they used a combo of lath and 
welded wire 8" out, but I will check again. And the tests I beleive were 
conducted with a more cementaceous plaster.
I will revisit this issue with our plaster guy. He likes using both lath and 
galvanized welded wire for various points in the walls.

You can see the tests at http://www.ecobuildnetwork.org/

Also as I recall, more fly ash may not always be better, and there may be a
point where the strength starts to go down.  I don't have the reference on
this, though.

John "Band Aid" Swearingen


John Swearingen
 SKILLFUL MEANS
design and construction
 www.skillful-means.com


-----Original Message-----
From: strawbale-bounces at listserv.repp.org
[mailto:strawbale-bounces at listserv.repp.org] On Behalf Of Leanne Rellstab
Sent: Tuesday, July 11, 2006 6:10 AM
To: SB List
Subject: [Strawbale] Welded wire mesh in Lime plaster


Doug wrote> I will put 2" square welded wire mesh 8" out from all wood
framing before plastering.

Howard wrote back: Sorry, why would you do that?  Of course, I have not seen
the plans so haven't a clue from what you've written what you intend.

Howard,

I saw a post here on the forum that led me to a study done in California
that tested plasters with welded wire mesh and without. Since they live in
an earthquake area in California it was a very important study. The results
showed that properly stapling welded wire mesh to wood framing increased the
shear strength of the walls by about 400%. The study also showed that welded
wire mesh extending out further than 8" into the plaster did not increase
the strength by any significance. So I decided to put 14 gauge galvanized
welded wire mesh into my structure.  We do have a few 4.0-4.5 Richter scale
quakes around here about every 10-20 years.

Lime plaster definitely has some great properties and I can't wait to work
with it. We will use either some Fly Ash or Volcanic Ash as the pusalon
(sp?). I heard second hand from a renound lime plasterer that some tests
were done with fly ash and lime to a ratio of 80% fly ash and 20% lime with
some amazing strength results. Of course it was experimental so I wouldn't
try it on our house. We will probably use what is normally accepted for
pusalon.

Thanks for the reply
Doug

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