[GSBN] Deconstruction

Joy Bennett mbenn1035 at yahoo.com
Sat Aug 1 13:32:13 CDT 2009

CASBA could kick in some dollars (for what they are worth these days) - just come up with a plan and a budget and we can see what we can afford - don't want to give you a number - just say what you need and we will see how much we can "grant".

It is these small little projects that can give us some neat information to affirm or deny some of the urban legends floating around.


Maurice and Joy Bennett

You must be the change you want to see in the world.   Gandhi

--- On Fri, 7/31/09, Tracy Vogel <tactileinteriors at hughes.net> wrote:

From: Tracy Vogel <tactileinteriors at hughes.net>
Subject: Re: [GSBN] Deconstruction
To: "(private, with public archives) Global Straw Building Network" <GSBN at greenbuilder.com>
Date: Friday, July 31, 2009, 2:14 PM

Re: [GSBN] Deconstruction

Sounds like a great opportunity.  I love deconstruction...

And I agree with everyone else’s input on what to document/test.  Do you happen to know or are you able to get the information on original application and the mixes?  As per Martin’s inference, with that information it might be possible to test the original plaster and compression etc and then have a base line to compare the failure to.

Keep samples, lots of them.  Of course they will change relatively quickly as well with drying and air flow and may be worth little shortly after demolition.

What are the parameters of the failure?  Was it localized or a full wall?  Was it only the top of the wall or all the way to the bottom?  Are you doing localized repairs or a rebuild of the wall?  Would it be possible to determine if the mold spores were from application or solely from the failure?  How far did the mold impregnate the bales, and the plaster?  Is the mold only on the straw/ fiber in the plaster?  Did the plaster have methyl cellulose or other binding additives?  If it is an exterior (or interior) wall was it sealed (with what) and therefore was it less permeable?  Was there a fine finish coat that also may have lowered permeability?  The plaster was up for 10 years right?  Is there anyway to determine how much water, at what rate, over what amount of time flowed through the wall?

How much do you think this may cost to assess?  I do think we could learn something here that is valuable although my preference for CASBA funding would be for full data sets that give us comparative analysis.  Data before and after in a realistic setting.

I look forward to hearing more.


Tactile Interiors

On 7/31/09 9:17 AM, "martin hammer" <mfhammer at pacbell.net> wrote:

On 7/30/09 11:32 AM, "Tim Owen-Kennedy" <timok33 at gmail.com> wrote:

I just started pulling apart an earth plastered straw bale wall that was damaged due to roof failure and there is actually some significant mold.  Going to document as much as possible . . . but wanted to know if any of you had any pet concepts or things you've always wanted to know about if you could just tear into a wall . . .

Tim, if it’s not too late:

In areas where you haven’t yet pulled off plaster, I recommend you drill a grid of holes in the plaster (one side only, maybe a 12” grid) in order to insert a moisture meter probe, and take readings 2” from each plaster face and in the center of the bale.  Then pull the plaster off each face and see how the visible damage correlates with the moisture readings.  

You could take the same readings after the plaster is pulled off, which would be a lot easier, but soon after the plaster is off, the moisture content of the straw (especially near the surface) might significantly change.  It may already have changed since the water intrusion incident, but there’s no way to go back in time (yet) (or maybe there is, and there are people among us who are from the future) (anyone on this list?).

Like Graeme I’d like to see an assessment of the steel reinforcement after 10 years in a weather-exposed earth plaster.


Like Dave Arkin I’m interested in saving plaster samples (ones that will yield as large a cube as possible) for compression testing.  Although I assume you don’t have compression values from the time of application for comparison.  Also, although it’s worth testing samples 10 years after application, I don’t anticipate compression values much different than a typical earth plaster tested 30 days after it was created.   I believe that once an earth plaster (or adobe brick, etc.) is fully dry, it has reached its maximum compressive strength.  It doesn’t cure and become stronger over time (even indefinitely) like materials with cement or lime binders.  It simply dries.

If there’s any additional costs associated with some of your “research” work, maybe CASBA could cover it?  With what has been discussed so far it doesn’t seem it would amount to much.

Thanks for requesting input, and I look forward to hearing what you discover.

Martin Hammer


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