[Greenbuilding] Cob as an alternative to spray foam sealant?

[natural building]

Frank, shrinkage depends on a number of factors and can range from  
between 5% all the way up to 50% for certain types of clay.  
Furthermore, the amount of moisture in the mix will affect the degree  
of shrinkage. That being said, as a 'rule-of-thumb' you can expect  
about 10% shrinkage in the clay content of your mix. If the clay is  
mixed with cellulose matter such as wood chips or straw, these will  
swell and shrink independently depending on the moisture in the mix.

My suggestion would be to try using two or three coats / applications  
with each successive layer filling the cracks and shrinkage that  
occurs in the previous.

Regards
Steve

www.naturalbuildingsite.net
naturalbuilding at shaw.ca

On 28-Jan-11, at 9:16 AM, Frank Cetera wrote:

> I'd like to know the same thing Steve (using a clay slip mixture,  
> what's the perlite for?).  Even if no one has ever attempted it, is  
> there anyone that can provide any professional opinion on the matter?
>
> Steve Satow, would it be a big deal if the cob shrank when it dried  
> when filling in shell air gaps?  If you dabbed the cob across any  
> gaps and left extra on the sides to shrink some?  How much does cob  
> typically shrink?
>
> "Ever since then,
> I've had the idea kicking around in my head to try a clay slip/perlite
> mixture sprayed into wall cavities like gunnite or shotcrete, anyone
> know if this has ever been attempted?
>
> I know it wouldn't be nearly as airtight or as insulating as spray
> foam, but it would be better than nothing and still completely
> biodegradable. :)"
>
>
> ~Frank
> www.alchemicalnursery.org
>
> Message: 5
> Date: Wed, 26 Jan 2011 13:53:51 -0800
> From: natural building <naturalbuilding at shaw.ca>
> To: Green Building <greenbuilding at lists.bioenergylists.org>
> Cc: Greenbuilding at bioenergylists.org
> Subject: Re: [Greenbuilding] Cob as an alternative to spray foam
>        sealant?
> Message-ID: <6EF75DF2-312E-47C8-9390-B75AEE63557E at shaw.ca>
> Content-Type: text/plain; charset="us-ascii"; Format="flowed";
>        DelSp="yes"
>
> Sheep's wool was traditionally used for caulking log homes.
> You can still buy it ( http://www.goodshepherdwool.com ) treated with
> Borax to make it more resistant to decay and fire (like blown
> cellulose insulation) and it might work better in cracks because it
> will swell, whereas cob is going to shrink as it dries.
>
> Regards,
> Steve Satow
>
> www.naturalbuildingsite.net
> naturalbuilding at shaw.ca
>
> On 26-Jan-11, at 1:40 PM, Frank Cetera wrote:
>
> > Is is doable to take wads of cob and seal up the cracks and air
> > seeps that are throughout the shell of the house?
>
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20110126/8e697471/attachment-0003.html 
> >
>
> ------------------------------
>
> Message: 6
> Date: Wed, 26 Jan 2011 14:15:22 -0800
> From: Steve <steve at greengeek.ca>
> To: Green Building <greenbuilding at lists.bioenergylists.org>
> Subject: Re: [Greenbuilding] Cob as an alternative to spray foam
>        sealant?
> Message-ID:
>        <AANLkTikHJ7gdqfLeXNr=KNOF4SjreNFa+ZA_VXmUZUzm at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> A couple of years ago I was talking with a relative about ways to
> build structures with modern techniques and traditional (natural)
> materials, and the subject of spray foam came up. Ever since then,
> I've had the idea kicking around in my head to try a clay slip/perlite
> mixture sprayed into wall cavities like gunnite or shotcrete, anyone
> know if this has ever been attempted?
>
> I know it wouldn't be nearly as airtight or as insulating as spray
> foam, but it would be better than nothing and still completely
> biodegradable. :)
>
> -Steve
> --
> http://www.greengeek.ca  
> _______________________________________________
> Greenbuilding mailing list
> to Send a Message to the list, use the email address
> Greenbuilding at bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20110128/91477ef9/attachment.html>