[Strawbale] Frost Heave-basement/cob

[Robert Tom]

On Wed, 21 Nov 2007 08:40:13 -0500, kim thompson  
<shipharbour at ns.sympatico.ca> wrote:

<snipped>

> The system/s I am considering are:
> 1. to fur out the rigid from the wall (with either wood or metal, or
> something else, spacers) then fasten the rigid  with concrete nailers
> or  2. "glue" the rigid directly to to wall with cob.
>
> then mesh the joints and apply a 1/2-1 inch local earth plaster (cob).
> I know that the earth plaster will adhere beautifully to the rigid
> thereby eliminating the need for gyproc or boards. It also provides a
> surface that helps to passively regulate relative humidity.

Kim;

I won't have a chance to write a lengthier reply until some time after  
Sunday but wanted to toss in a couple of thoughts in the meantime.

First of all, WRT insulation.

If the intent of the earth plaster is for humidity buffering (not I didn't  
say control because I don't think it can) then "more" is better. (ie I'm  
not sure 1/2 - 1" would do much to that end.)

So if a thicker earth plaster is used (say 3" or more), then the need for  
the rigid (presumably foamed plastic) as a plastering substrate becomes  
less or un-necessary.

Then semi-rigid Roxul mineral wool becomes more feasible.

It would also be possible to build a 2x3 steel stud wall spaced out from  
the foundation any desired distance to accommodate a thick, overlapping  
layers of Roxul batt insulation, creatign a continuous layer of insulation  
under the steel studs, the steel studs could then carry any necessary  
services without being concerned about creating cold spots/thermal bridges.

Then if desired, semi-rigid Roxul could be attached to the steel studs to  
serve as a temporary backstop for plastering, with your choice of a mat or  
lath (Nova Scotia "bamboo" ?) furred out from the Roxul board to reinforce  
the earthen plaster, if necessary.

Sheet steel Z-channels can be used to provide fastening points at the  
surface of the Roxul board.

Or the rigid Roxul could be completely eliminated and the lath (whatever  
it may be) attached directly to the steel studs, but furred out from the  
face of the studs to allow full embedment of the lath.

But insulating on the inside in the above manner does have consequences at  
the outside of the foundation. If poorly drained moisture in the  
surrounding soil, deprived of heat loss from the foundation, will likely  
freeze and if that happens, frost damage could occur.

Obviously, the best solution would be to first fix the poor drainge and if  
one is doing that, then one might as well insulate on the outside, the  
optimal location.

More later if necessary.



-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at chaffY a h o o  dot  c a >
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