[Cob] Lime Render - FAILURE

[Bill Wright]

Hi All,

Please refer to Shannon's email (included here - below this email), and to this. . . 

Which is a response from her regarding the idea of using a, "coating" over the lime, 

FROM SHANNON:
". . .I would be very wary of any coating over your wall which might tend to waterproof it. There is a long history (in all building techniques - bale, adobe, cob, wood frame, metal frame, brick, ...) of waterproofing causing more damage than it prevents. Water (via condensation of water vapor) will get into your wall! The question is whether or not it can easily get out before it causes damage."

IN RESPONSE TO SHANNON'S TWO EMAILS INCLUDED HERE IN THIS EMAIL, I WOULD LIKE TO SUBMIT THE FOLLOWING NEW PHOTO TO OUR DISCUSSION:

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.

The question I'm sitting with. . . Will lime-putty in the cracks, and a lime wash on top of that be the best fix? 

The other potential idea on the table is to take the above step a step further. . . 
That is to put a TOP COAT (of some type) over the lime-containing render after we fill cracks, and lime wash the building. 

Onwards and thanks!
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 20, 2017, at 3:10 AM, Shannon Dealy <dealy at deatech.com> wrote:
> 
> On Fri, 17 Feb 2017, Bill Wright wrote:
> 
> [snip]
>> I've listed the brown and finish coats here previously, and the wall in question is a 100% cob wall. What IS there as well, helping form the curve in the wall, and helping the cob/brown coat/finish lime coat connect to the framing for the doors is. . . Expanded Metal Lathe. So the layers in sum are: Cob wall, expanded metal lathe bridging the wooden door frame to about 12" onto the cob wall, and screwed into the cob wall w/ 3.5" deck screws, brown coat, finish lime render.
> [snip]
> 
> One additional thought, look at the areas which aren't showing signs of cracking/flaking. Presumably this is the majority of your building? If so, think of these as places where you got the job done correctly and ask yourself what are the differences between those areas and the places where you are having problems. Your issues may not be current issues, but may have happened during the initial application and simply taken time to become visible.
> 
> Things to consider might include:
> 
> - Differences in the wall surface under the plaster  (such as the metal
>   lathe - I've never used it so I have no idea what, if any issues it
>   might raise)
> 
> - Differences in airflow patterns across the building. Areas exposed to
>   prevailing winds or just unusual wind patterns at the time of
>   application may end up drying much faster than more protected parts of
>   the building, which can cause the problems you are seeing.
> 
> - Differences in sun exposure which can also cause drying to be too fast.
>   This difference doesn't have to be how the sun hits the building such
>   as North versus South side (though it may be), it could simply be the
>   time of day in which the application was performed.  If you applied in
>   mid day sun versus evening.
> 
> - Differences in how you protected the surface after application such as
>   misting the area periodically, hanging a tarp over it, etc.  Perhaps
>   some days you had to leave the site immediately where for others you
>   were around for a while to keep the new plaster moist.
> 
> - Finally (typical of my work :-) seasonal differences if you do the job
>   piecemeal, completing part of it in one application, then becoming too
>   busy so the next part was done weeks or months later when the humidity
>   or other environmental factors are different.
> 
> FWIW.
> 
> 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