[Strawbale] Frost Heave-basement/cob

[kim thompson]

Hello all,

I have been following the discussion of frost heave with considerable  
interest, hoping that it might align with a project I am about to  
embark upon, but the thread is not quite there, so I would like to  
add another twist to the conversation and would appreciate all  
comments anyone might have on it.

Basically am trying to wrap my head around the building science side of
what the pros and cons are of installing rigid (eco friendly, of  
course) insulation on the interior side of basement walls and  
plastering on them with earth? Am hoping a system/s will emerge that  
offers a simple and affordable treatment that might make a huge  
difference in renovations  for older buildings.

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.

The case I am considering a two storey wood frame home built in 1930.  
The house and the basement are very dry and sound with a cement slab  
floor. The basement is used for laundry, workshop and storage  
(especially of the furnace). Three-four feet of the walls are above  
grade and there are small windows on three sides. It is just high  
enough that any one under 5'10" can move around (mostly) without  
bumping a rafter or pipe. The oil furnace heats the water pipes that  
run along the rafters to the cast iron radiators upstairs. These  
pipes give off a fair bit of heat to the basement before going up.

As I understand it below grade walls serve many functions i.e.  
providing a foundation which mitigates frost heave issues for the  
rest of the building, it  also (amoung other things)  provides  
thermal mass and acts as a heat sink for ambient ground heat.

New building practice is to insulate to the outside of the  
foundation, whether it is following the foundation wall or panning  
out from the perimeter as for shallow insulated slabs. What are the  
potential problems of insulating to the interior, if any??

Thanks so much for your thoughts on this.

 From the hearth,

kim


NOTE: one thought with the spacer system mentioned above was that in  
instances where basement walls are not damp proof  (i.e. in a flood/ 
heavy rain situation) the rigid would act as a kind of rain screen,  
and if there was appropriate drainage in the floor, could help  
minimize damage to the basement by directing water away from the  
building.

Kim Thompson
Straw Bale Projects
e mail: shipharbour at ns.sympatico.ca
www.naturalbuilding.ca

"Tradition and modernity are merely two sides of the same coin - and  
must be dealt with simultaneously. Building cannot be a rigid dogma,  
but a living, organic, ecological project. It is about continuity,  
based on memory, common sense and experience and is the foundation of  
invention."   Hasan Uddin Khan


On 21-Nov-07, at 7:59 AM, Hank Carr wrote:

> Hank Carr wrote:
>
>>> With rubble trench and slab foundations the building should be  
>>> heated
>>> in the winter whether you are living in it or not to keep the ground
>>> under the building thawed and to prevent heaving and cracking.
>
> Speireag Alden wrote:
>
>> Rubble trench foundations are the whole reason I replied to this
>> thread, since I built my house on one, and they interest me, and your
>> 11/12 remark seemed over-broad to me.
>