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

Fri May 12 19:29:14 CEST 2006

Hi Michael

thanks for your reply.

By coincidence I found  a link this to a pilot study from Canada which 
highlights my basic concern expressed in my original post, you might be 
interested.

Pilot Study of Moisture Control in Stuccoed Straw Bale Walls | CMHC
http://www.cmhc-schl.gc.ca/en/inpr/bude/heho/heho_004.cfm

Its a study of cement stucco finished straw bale walls and the possible 
negative effects this could have in trapping moisture in the wall, promoting 
problems with damp.

My concern is that in colder climates clients/homebuilders go for "security" 
and put on a cement render for protection against the elements when its 
possible this might cause problems in the future. I would be genuinly 
interested to know what percentage of reported failures of straw bale 
structures were cement stuccoed.

There is a classic case froma few years back in the UK. A couple built a 
straw bale house which was followed on a programme on  national TV. The 
architect decided the prudent approach was to cover the outside in weather 
proof cladding, metal cladding. Interstitial condensation and the straw 
started to rot. The cladding was replaced but of course most people just 
remember the straw  rotting unfortunately

abientot
Paul

>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] 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 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 
>>>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
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>
>
>
>____________________________________________________
>    European strawbale building discussion list
>
>Send all messages to:
>Strawbale at amper....muni.cz
>
>Archives, subscription options, etc:
>http://amper.ped.muni.cz/mailman/listinfo/strawbale
>____________________________________________________
>
>