[Cob] lime render fail or just wet?

[Bill Wright]

HI Gena,
All the responses have a bit of gold in them.
Thank you!
Bill

Bill Wright, L.Ac., DNBAO
Wright Acupuncture and Massage
251 Auburn Ravine Rd., Ste. #205
Auburn, CA 95603
530-886-8927
"There is no path to healing, healing is the path" 


> On Feb 26, 2017, at 10:35 AM, Gena Arthur <genaarthur at hotmail.com> wrote:
> 
> Hello,
> 
> I have a small strawbale cottage and when the prevailing winds blow rain into the lime render it does appear wet as well. Not sure if that is helpful or not. 
> 
>> On Feb 26, 2017, at 2:01 PM, "coblist-request at deatech.com" <coblist-request at deatech.com> wrote:
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>> Today's Topics:
>> 
>>  1. Re: Lime Render - FAILURE (Shannon Dealy)
>> 
>> 
>> ----------------------------------------------------------------------
>> 
>> Message: 1
>> Date: Sun, 26 Feb 2017 14:56:44 +0100 (CET)
>> From: Shannon Dealy <dealy at deatech.com>
>> To: coblist at deatech.com
>> Subject: Re: [Cob] Lime Render - FAILURE
>> Message-ID: <alpine.DEB.2.11.1702261456150.25248 at nashapur.deatech.com>
>> Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
>> 
>>> On Wed, 22 Feb 2017, Bill Wright wrote:
>>> 
>>> https://www.dropbox.com/s/2657yta5fpeyec2/Photo%20Feb%2021%2C%208%2000%2037%20AM.jpg?dl=0
>>> 
>>> DISCUSSION OF PHOTO:
>>> You can see in the photo that the lime-containing render is getting saturated 
>>> with the water from rains blowing onto the building where the prevailing 
>>> winds are doing their work. IS THIS PROOF that the mechanism at play here is 
>>> water making its way through the lime-containing render into the earthen 
>>> brown coat below, and the swelling action of the deeper middle layer cracking 
>>> the lime-containing outer render? It appears that way to me.
>> 
>> I'm afraid that all this really tells us is that the wet surface looks 
>> significantly different from the dry surface. It doesn't tell us anything about 
>> the depth of penetration. There are similar differences between wet and dry 
>> areas on the outside of three buildings I have which are just bare cob walls 
>> (over 10+ years exposure on all three buildings). Of course since I haven't 
>> plastered there is no outer layer for the water to get beneath, however, my 
>> bare walls are far more absorbant than the plaster mix you describe is likely 
>> to be.
>> 
>> I'm afraid the only way I can think of to get more information is to pick a 
>> spot in a wet area without any nearby cracks, dry the surface of the 
>> surrounding area with a towel, cut a hole through the plaster with an
>> old chisel and see how deep the moisture goes. You should also be able to tell 
>> how well the plaster is bonded to the wall in this area.
>> 
>>> The question I'm sitting with. . . Will lime-putty in the cracks, and a lime 
>>> wash on top of that be the best fix?
>> 
>> This would certainly be my approach, though I would use a lime-sand mix with 
>> fine sand rather than straight lime putty to fill in large cracks
>> (sand reduces/prevents shrinkage). Ideally you want your patch mix to match 
>> your surface as much a possible and refloat the surface to blend the patch in. 
>> The lime wash is a good idea, but will not hide any significant differences in 
>> the appearance of different areas of the wall (that takes time and multiple 
>> coats).
>> 
>> One thing I just realized, you didn't mention any kind of fiber in your plaster 
>> mix. While plasters can be done without fiber, using fiber can greatly reduce 
>> the chances of cracking, particularly fine cracks.
>> 
>> 
>> Shannon C. Dealy               |       DeaTech Research Inc.
>> dealy at deatech.com              | Biotechnology Development Services
>> Telephone USA: +1 541-929-4089 |      USA and the Netherlands
>> Netherlands:   +31 85 208 5570 |          www.deatech.com
>> 
>> 
>> 
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>> End of Coblist Digest, Vol 15, Issue 9
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