[Cob] Lime Render - FAILURE (Bill Wright)

[Tys Sniffen]

While there are a zillion variables to plasters and how they sit, I would say that the greater moisture this year only helps your situation - making the different materials more flexible and pliant, able to move a bit with each other. 

What I've found, with an interior lime plaster over natural clay scratch coat on top of cob is that the lime plaster seems more brittle than the clay stuff.  my clay plasters and cob move a bit with settling, and the crack shows up only in the lime plaster - on the surface.  

My cob house seems to be still settling, about 8 years after completing the cob.   It's just a tiny bit, but the cracks show up in the final plaster with lime in it, in a few joint like places.  

Note I only really have the experience of my own house, I'm not a repeat builder.
Tys



-----Original Message-----
From: Coblist [mailto:coblist-bounces at deatech.com] On Behalf Of coblist-request at deatech.com
Sent: Friday, February 17, 2017 10:00 AM
To: coblist at deatech.com
Subject: Coblist Digest, Vol 15, Issue 2

Send Coblist mailing list submissions to
	coblist at deatech.com

To subscribe or unsubscribe via the World Wide Web, visit
	http://www.deatech.com/mailman/listinfo/coblist
or, via email, send a message with subject or body 'help' to
	coblist-request at deatech.com

You can reach the person managing the list at
	coblist-owner at deatech.com

When replying, please edit your Subject line so it is more specific than "Re: Contents of Coblist digest..."


Today's Topics:

   1. Lime Render - FAILURE (Bill Wright)


----------------------------------------------------------------------

Message: 1
Date: Fri, 17 Feb 2017 09:43:09 -0800
From: Bill Wright <bill at auburnacupuncture.net>
To: coblist at deatech.com
Subject: [Cob] Lime Render - FAILURE
Message-ID:
	<E2A46CF4-BED9-44FD-AA2F-8DD9066AB891 at auburnacupuncture.net>
Content-Type: text/plain;	charset=us-ascii

Happy New Year of the Fire Rooster All!

I'm attaching photos here for you to view online (below my message ;^).

The images show the cracking of a lime render applied less than (1) year ago over an earthen brown coat. The Brown coat was 3 parts sand to 1 part - 90% indigenous site clay and 10% lime (NHL 3.5). The final lime render was 2.5 parts sand to 1 part - 90% lime (NHL 2.0) and 10% indigenous site clay. A pigment from Trans-Mineral USA was added for color to the recommended acceptable amounts according to the manufacturer of the pigment. (I think TM USA was the source, I know we got our lime from them - St. Austier NHL). 

My Natural Home Builder and I believe that the greater than average rains in Northern CA this winter have saturated the lime render to the point of moisture moving thru the lime to the clay brown coat underneath; which is expected, and not usually a problem. . .  Not a problem UNLESS the clay expands and cracks the lime render above; which we believe is the mechanism of how the lime is cracking.

The real problem is two fold:

A. I'll bet my bottom dollar the County will not pass my building w/ cracks in the render - big ouch!

B. The process of water expanding the clay underneath is progressing to the point that the lime is delaminating and falling off in certain areas. While this is not really a huge structural issue, it's a bummer, and it's unsightly to say the least. Over time, it could start to wear down the cob/earthen layer beneath it, which will create more work to fix it.

So, my question is this. . . What would you do next to remedy this situation and create a functioning wall given my current situation?

PICTURES:

https://www.dropbox.com/s/ib58lvdq5crtly4/File%20Feb%2017%2C%207%2059%2025%20AM.jpeg?dl=0

https://www.dropbox.com/s/5y52e8x455ngiuv/File%20Feb%2017%2C%208%2000%2012%20AM.jpeg?dl=0

https://www.dropbox.com/s/uwfe9b638zsi1z4/File%20Feb%2017%2C%208%2000%2055%20AM.jpeg?dl=0

https://www.dropbox.com/s/ut8bxeksxbhb2y4/File%20Feb%2017%2C%208%2001%2023%20AM.jpeg?dl=0

Many 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" 



------------------------------

Subject: Digest Footer

_______________________________________________
Coblist mailing list
Coblist at deatech.com
http://www.deatech.com/mailman/listinfo/coblist


------------------------------

End of Coblist Digest, Vol 15, Issue 2
**************************************