[Strawbale] re RE: The BIG question (Michael Lough)
michaelklough at sympatico...
Thu May 11 15:40:35 CEST 2006
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
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.
>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
>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 at sympatico...>
>>Reply-To: mkl18 at pobox..., European strawbale building
>>discussions<strawbale at amper....muni.cz>
>>To: strawbale at 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
>>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
No resolution, no rockingthe boat. Time perhaps unfortunately will
But then again I may be "outside" the truth. There is doubt here in
>>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
>>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
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