[GSBN] School built in Nepal - Seek for advise

Fri Jun 20 20:22:12 UTC 2014

Hi Sona,

We also had a problem with spots on a project we did in Pakistan in 2009.  The first photo is of an interior 6" thick wattle and daub wall.  The second photo is of a 6" thick clay/sand/straw plaster over a concrete block retaining wall (note the wall transitions to straw bale above the shelf).  The photos were taken in April, so the walls were drying on the slow side.  Surkhab (PAKSBAB's COO) told me that when the walls finished drying, the spots went away.  They were then painted with limewash, a typical process for us.  There weren't any spots on the straw bale walls, which had thinner plaster (about 1 1/2").  Therefore I suspect thick plaster/slow drying was the culprit in our case.

I suppose if the spots don't totally go away and you want a natural clay finish, you could try painting the walls with a clay paint.  

I agree with Graeme's comment about the exterior cement paint.

Darcey

Darcey Donovan, P.E., C.E.O.

Pakistan Straw Bale and Appropriate Building (PAKSBAB)

P.O. Box 1083

Truckee, CA 96160 USA

+1-530-902-5516 Ph

darceydonovan Skype

darcey at paksbab.org 

www.paksbab.org

From: GSBN-bounces at sustainablesources.com [mailto:GSBN-bounces at sustainablesources.com] On Behalf Of John Swearingen
Sent: Thursday, June 19, 2014 6:29 PM
To: Global Straw Building Network
Subject: Re: [GSBN] School built in Nepal - Seek for advise

I second Matts' whitewash idea.  If it works for politicians, it should work to keep us Out on Bale.

John "Whiter whites and Greener greens"  Swearingen

On Thu, Jun 19, 2014 at 5:14 PM, Matts Myhrman <mattsmy at gmail.com> wrote:

Wondering if a lime wash would delete the spots permanently.  Easy to test in a small area.  Would also lighten up the space.

Matts (If all else fails, whitewash it) Myhrman at (Still) Out On Bale.

On Thu, Jun 19, 2014 at 4:57 PM, Graeme North <graeme at ecodesign.co.nz> wrote:

Hi James

The spots look like a very typical interaction that sometimes happens between wet clay and organic matter - and is most likely the result of a fermentation process in action.

It can take months for the stains that can result to develop as moisture migrates through the material, as you have found out. The end result from fermentation usually toughens up the wall material, but if uneven fermentation takes place within the wall, will typically cause staining. It appears that it may be related to the position of the bamboo that is nearest the surface of the wall, i.e. where the daub is thinnest, for some reason that eludes me.

It is not harmful but can be persistent, and can look disfiguring. 

Not a very nice idea, but bleach can sometimes remove these marks.

I think that the very worst thing would be to put a cement based anything on the interior of these walls - that will stop it breathing, trap moisture within the wall, and could lead to all sorts of problems, esp if the spots are related to ongoing moisture migration of any kind within the wall.  I am not sure of the traditional houses are now typically rendered on the outside with cement paint, but if they are not, and do not get spots on them, then this may point to the cause and a solution too, as cement based paint will act as a moisture barrier and hold moisture within the walls. 

The traditional render sounds good to me. If it cracks the addition of more aggregates should help, i.e.  adding in more rice husks and fibre, or sand if any is available.

After 6 weeks the plaster should have fermented nicely and give a nice even colour! 

Maybe this may help

Graeme 

Graeme North Architects

49 Matthew Road

RD1

Warkworth 0981

tel/fax +64 (0)9 4259305 <tel:%2B64%20%280%299%204259305> 

www.ecodesign.co.nz

On 18/06/2014, at 8:43 AM, James's <james.henderson8 at bigpond.com> wrote:

Does anyone have any ideas for Sona?

Thanks James

Sent from my iPad

Begin forwarded message:

From: Sona Huberova <sonahuberova at yahoo.com>
Date: 16 June 2014 9:47:39 AM AEST
To: James Henderson <james.henderson8 at bigpond.com>
Subject: School built in Nepal - Seek for advise
Reply-To: Sona Huberova <sonahuberova at yahoo.com>

Dear James,

my names is Sonia and we met at the EBAA conference last year, we are the couple with the school in Nepal. I have to organize fixing some defects on this first building now and would like to ask for your opinion in one particular matter. I just started to read your book so I thought that you may be able to help us. 

As you may remember, the school is built with bamboo frame and wattle and daub walls, weaved and plastered from two sides. After a couple months, spots appeared on the inside of the walls, you can see in the attachment. The spots are not seen on the outside, but we think that it is because the facades were painted with cement-based paints at the end of construction, which did not happen in the interiors.

We are planning to fix the spots by painting the interiors with similar paint, although I am not sure it will solve it for good. But we are puzzled why did the spots appear in the same place. We let the villagers to mix and render the walls in their traditional way, so the mixture is as follows:

3 parts of soil (half in half mixed from two soils, one more clayey, one less) 

1 part of rice husks

1 part forest grass finelly chopped

1 part cow/buffalo dung

The mixture has been left to rest for six weeks or more. We were told that this is the traditional way to render, and the mixture indeed was very strong after drying, alhough cracked a lot and two more coats were needed to finish it. I am not sure what sort of mixture they used for the final layers, but it would againg be just a combination ot the above mentioned.

Some of the walls were then filled with loose soil, but we abandonned this so not all of them are. the spots appear on the filled one as well as on the empty ones.

We are surprised at finding the spots as none of the local houses, rendered in this traditinal way have this problem.

Would you have an idea what may have caused it? Have you ever encountered or heard of this sort of spotting?

Bamboo elements were pressure-treated with solution of Acid Boric and Borax, do you think that may be the problem? 

We are planning to build more of those school buildings in Nepal based on a standardized project, so we will need to avoid the defects and their causes in future.

Sorry for bothering you with it and I would understand if you did not have time to answer to me.

Kind regards

Sona Huberova
+61 466 482 682 <tel:%2B61%20466%20482%20682> 

meemARCHITECTURE

www.meemarchitecture.org <http://www.meemarchitecture.org/> 

<Classroom walls_1.jpg>

<Classroom walls_2.jpg>

<Classroom walls_3.jpg>

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-- 
John Swearingen
Skillful Means Design & Construction
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510.849.1900 fax

Web Site:  http://www.skillful-means.com
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