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Re: GSBN: Lime plaster problems



Actually, John, Andy in Cape Town, South Africa would need to move the
project north to a warmer climate...

Andy, I wish I had more direct experience to be able to offer you some
advice or guidance, but I know that there are many people on this list
who have more of that I do and hope they chime in with it soon. I wish
you good luck with the resolution and applaud your willingness to share
the experience so that hopefully we can all learn and benefit from it.

Warmest regards,

David Eisenberg
www.dcat.net

-----Original Message-----
From: John Swearingen john.skillfulmeans@...
To: GSBN GSBN@...
Sent: Wed, 26 Sep 2007 11:57 am
Subject: Re: GSBN: Lime plaster problems

Andy,

It seems to me that major problems were weather related, the drying
wind and
freezing. You don't say just how smooth the earth plaster was before
lime
was applied. If it's a porous material the lime would be able to adhere
even
without scarfing.

The lime plaster needs to be removed in any case, and you could no
doubt get
some teenagers to deface the surface of the earth plaster for a small
fee.
Then try again in warm weather, or move the building south to a warmer
climate.

John

On 9/26/07, Andy Horn andy@... wrote:

Dear all

Dear all
I know this is not strictly a SB question, but rather one of lime
plaster
...but really could do with some experienced input.

I recently was involved in the building of a large 2 storey mud brick
school
classroom...in a rural part of the country. To help protect the walls
we
applied an earth plaster followed by a coat of lime plaster on the
weather
side. We used a hydrated lime and added plaster sand together with a
small
amount of the adobe soil to the mix. We applied the plaster and as
soon as
it had set applied a colour "fresco" wash for a gorgeous looking
finish.
We
also rewet the wall continuously for good curing, but were not
equipped
with
proper scaffolds and drop sheets to cover the walls from the sun and
wind
...and made do with a large sail that was precariously positioned
around
our
2 scaffold towers.

While applying the plaster, we ran into a number of difficulties. The
wind
suddenly picked up and was drying the plaster out excessively quickly,
leading to much cracking. So we had to rework the cracked surfaces to
get
the cracks out. On the first morning after applying the plaster the
weather
turned at night and brought frost...2 months ahead of when it is
normally
expected! There were sheets of ice in the water buckets that morning!

A few weeks later, it turned out there were major problems with the
plaster
delaminating from the walls, (see below).

The supervising architect wants to know what to do....and is being
advised
to strip off the existing plaster and attach a chicken mesh around the
structure and reapply the lime plaster. I am not keen using the
mesh....don't think it is needed if there is no cement in the plaster.
Also
it can rust and will be expensive. The whole idea with the project
was to
train the locals in simple inexpensive methods they can employ on
their
own
structures.

If anyone has some insights to share or advice as to how we can do it
better, I would most appreciate your inputs. Maybe we should have
done 2
coats....The base earth plaster coat was due to a miscommunication on
site
was not provided with a proper key....and we were not sure how to
provide
one with the earth plaster already hardened, without damaging /
impairing
its strength. Any ideas for how best to do this....drill holes, angle
grind,
soften with water and saw cuts...???
I also have pictures I can email to you directly if you want to get a
better
idea of the problem we are facing

Your inputs would be much appreciated

Kind regards
Andy Horn


-------------------------------------------------------------------------
---
--------

Hi Andy

Here are some photos taken earlier today of Block B.

Owen, Dave Osborn & I all agree that there doesn't appear to have
been a
proper bond between the lime plaster and the earth plaster. The
surface
treatment of the substrate appears to be too smooth for bonding to
take
place. The bad news is that there are large 'hollow' areas - at least
50%
of
the plastered surface. We all agreed that a good solution would be to
strip
the plaster off and nail/staple a layer chicken wire onto the
substrate
before replastering. I guess that we should have scratched the surface
deeper before we applied the plaster. Weather conditions could also
have
played a role. The lime plaster layer is approximately 10mm thick and
appears to be strong.
Please give me your thoughts on this.

Regards

Steve




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--
John Swearingen
Skillful Means, Inc.
Design and Construction
www.skillful-means.com


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