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[Strawbale] re RE: The BIG question (Michael Lough)






Hi Michael,
The original qoute I responded to said failures reported in NE America. I didnt say all buildings in America were ciment rendered 

sorry my misunderstanding?
just my observation that quite a few have been, especially in cold snowy areas like the NE.
well Canada qualifies I think in this regard and Portland/Lime mixes are considered acceptable here by a few. The issue seems to be whether or not testing was done on the long term effects of using a non permeable material in sufficiently high quantities in a bale render allowing for convection currents within the bale wall assembly itself. I havn't seen anything on this here and have only read of experiments in Europe. 





A stucco plaster is called stucco
Thanks for this. I have been labouring under a misunderstanding. A quick check proves you are in fact correct.
I thought for a while that I should crusade on behalf of the word cement as it seems it is a word that has come to mean Portland cement whereas it was originally meant to mean something more broad as in cementitious but realised the futility of it eventually .
I understand that in drier areas like Arazona, clay or lime based plasters are used, in colder, wetter areas ciment/lime finishs are more ususally used. 

Not sure if it is quite that cut and dry not having the figures
It is a shame that there does aopear to be a tendancy to try and ignore problems/failures in in case the "cause" is damaged. I think there is a tendency to panic at the eleventh hour and put on a ciment based finish.
It is a difficult question and perhaps there is no easy answer. If one wished to why not build for a short building lifetime with recyclable materials? If the walls rot take the house to pieces and build again. perhaps the idea of "permanence" established in European culture as a desirable necessary quality for a building is less developed in North America where hunter gatherers lived in animal hide mobile structures not so long ago. The advantage of using lime/sand only can perhaps only be realised (or not) through experience and the only true test, that of time perhaps. 


adios

Michael











Hi Michael,
The original qoute I responded to said failures reported in NE America. I didnt say all buildings in America were ciment rendered, just my observation that quite a few have been, especially in cold snowy areas like the NE.
A stucco plaster is called stucco because it contains either lime sand mix which is the original method or the modern ciment/sand mix, in the UK called a render. Gypsum based plasters are called plasters not stucco. 
"
I understand that in drier areas like Arazona, clay or lime based plasters are used, in colder, wetter areas ciment/lime finishs are more ususally used.
It is a shame that there does aopear to be a tendancy to try and ignore problems/failures in in case the "cause" is damaged. I think there is a tendency to panic at the eleventh hour and put on a ciment based finish. 


From: "Michael lough" <michaelklough@sympatico...>
Reply-To: mkl18@pobox..., European strawbale building discussions<strawbale@amper....muni.cz> 
To: strawbale@amper....muni.cz
Subject: [Strawbale] the BIG question
Date: Wed, 10 May 2006 04:48:42 +0000

sorry for lateness in replying but have been distracted recently?
"There have been reports of "failed" straw walls in NE America with some admitting the damage was likely caused by dampness but no admission of the dampness being caused by convection currents within a wall, therefore no remediation has been undertaken as it has not been proved. Which of course means here "business as usual"
+++I wonder how many of these failed walls were plastered with a cement based render/stucco? 
I know the Americans like their straw bale buildings cement stuccoed.
A generalisation I'm afraid. It is true that Portland/Lime mixes are used and one Strawbale commercial group in Canada has even accepted web "sponsorship" from a Portland cement manufacturer but Portland use in plaster is not the case all over North America. In the US there are quite a lot of Lime/sand plastered structures I believe. The heritage of straw bale appears to me at least to be more Arts/craft conscious less "industrial" than in Canada.
The issue of Portland containing plasters (not stucco, that is gypsum based I believe) and the effect it may create once on straw over time in a humid region is one I am not that informed on. But it appears that the test of time is underway. One hears of problems and discussion and then nothing?No resolution, no rockingthe boat. Time perhaps unfortunately will tell?But then again I may be "outside" the truth. There is doubt here in quiet corners. 

The real problem is the cost of real industrial testing of straw bales.
++I think if you are going to use an organic material in a buildings structure, provision for air movement through that structure becomes paramount, even at the loss of thermal performance.
It depends on the amount of the moisture in the air and at what point does this warmed moist air come into contact with outside conditions which will then turn the moisture back into water? This is the question. The dew point can move with the seasons also.
What could happen if say heat went into plaster from the inside which warms the air immediately inside the bale Will this heat rise through the bale(s) If there is air inside the bales why wouldnt it? And would this air form a convection current inside the bales albeit a slow one. If the outside is cold then the warm air would meet the colder outer bale inside surface at some point and condensation would result ?? Would Portland allow for "expiration"? Doubtful as it is used for swimming pools?
++"sealing" in a straw bale wall with cement plaster seams like asking for trouble unless it is a dry climate.
I share your instincts.Many others do as well. In Canada the potential for problems is not seemingly acknowledged by everyone .
It would be interesting and very useful to have a reference to straw bale wall "failures" to learn from, is anyone making a comprehensive record of these situations? 

let it move, let it breathe!
The single most important problem of building with straw bales is not the subject of a permanent record. (not one that I have seen anyway)
It seems as though the collective attitude is to not give straw bale construction a bad name while these problems are discussed quietly. The trouble is that there are some perhaps less scrupulous individuals that believe that no apparent discussion means no problems which means using Portland is OK. 

its all a bit disturbing ?

regards

Michael