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

Mon May 15 18:18:22 CEST 2006

Paul

The concept of interstitial condensation is well known. This is likely
to occur when the outer face is sealed. However in recent times the
construction industry has been using the concept of rain screen
cladding, that is, the cladding acts almost like a vertical umbrella,
allowing air movement behind the cladding but shielding the structure
from rain.

I assume the metal cladding you refer to was effectively sealed.

Do you have any further info?

Regards

Eric Larmett
Senior Engineer

Arup Building Engineering
St James's Building, Oxford Street, Manchester M1 6EL
tel:           +44(0) 161 228 2331
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eric.larmett at arup...
www.arup.com 
-----Original Message-----
From: strawbale-bounces at amper....muni.cz
[mailto:strawbale-bounces at amper....muni.cz] On Behalf Of paul sheraton
Sent: 12 May 2006 18:29
To: strawbale at amper....muni.cz
Subject: RE: [Strawbale] re RE: The BIG question (Michael Lough)

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
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>
>
>
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