[Strawbale] Gypsum plaster over stucco

[Jeff Ruppert]

Craig,

You will need to apply a bonding agent, sometimes called "plasterweld", 
to the cement base coat before applying the gypsum.  It is like Elmer's 
glue, but either pink or blue.  This is mainly to keep the warranty 
intact for the gypsum product, but also the make sure there is a good 
bond between the two dissimilar materials.  I have heard of a case where 
no bonding agent was used with mixed results.

Unless you are in a cooling climate, reducing the permeability of the 
interior surface of your bale walls will probably be ok.  You want to 
keep interior humidity from entering the wall, while allowing any 
built-up moisture to exit to the exterior.  Basically, you can seal the 
interior surface without any problems, just don't do it on the exterior.


Jeff Ruppert, P.E.
Principal

Odisea LLC
Engineering and Consulting

Front Range Office 		West Slope Office		
1731 15th St. #105		337 Main Ave.
Boulder, CO  80302		Paonia, CO 81428
303.443.4335			970.948.5744
303.443.4355 f			1.866.795.6699 f
jeff at odiseanet.com
www.odiseanet.com


Hillman, Craig wrote:
> I'm looking for some feedback based on theory or experience with using a
> gypsum-based plaster as an interior finish coat over cement stucco.
> 
> The owner/builder/contractor that I am working with has asked the local
> suppliers for input, and been told to use primer sealers or other
> products that would further limit the ability for the wall to allow
> vapour permeability.
> 
> I know that Erica and Mike used something like this on their former home
> in Fernie, BC with beautiful results.
> 
> Any thoughts on what should work? More importantly, are there any
> pitfalls to avoid?
> 
> Craig
> 
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