[Greenbuilding] Salt and Concrete Sealer-flavoured Chips, anyone?

[Chris Green]

Keith Winston wrote:
> Typically, you don't want waterproof finishes on strawbale, as far as 
> I've ever heard. Breathable lime or earth plasters allow it to dry. I 
> think you're not even supposed to use a portland cement based stucco, 
> much less a totally waterproof cement.
>   
Ideally, one would use an earthen plaster, or an earthen-lime plaster, 
followed by the lime, then the PC render. But not everybody lives and 
works in an ideal environment. I'd be really challenged to find usable 
deposits of clay in this area, and I have been looking. I think if 
someone did a survey, most of the SB homes built in Canada do have a 
portland cement based finish.

You do want some kind of waterproof finish on the exterior surface if 
the building is liable to be impacted by liquid water. The sodium 
acetate should prevent the liquid entering the wall, but one it's dry it 
would allow moisture vapour inside the wall to exit. Kind of like a 
one-way valve, so to speak. At least that's my impression of it  at this 
moment.  And that one-way valve potential for the sodium acetate 
treatment is why I think this stuff should be tested.

There is the potential to merely waterproof the bottom 2 to 4' of a 
rendered wall, since that is most likely to be the area impacted by 
sprinklers and splash-back, leaving the top half or 2/3's somewhat more 
pervious to moisture vapour transmission. Of course, the likely result 
would be the building has tone-tone finish, and that could have some, 
um, interesting...design possibilities.

Cheers,

Chris Green.