From: "Michael lough" <michaelklough@sympatico...>
Reply-To: mkl18@pobox..., European strawbale building
discussions<strawbale@amper....muni.cz>
To: strawbale@amper....muni.cz
Subject: [Strawbale] re RE: The BIG question (Michael Lough)
Date: Thu, 11 May 2006 13:40:35 +0000
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
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