[Strawbale]Earth/Straw plaster acting as fire guard

[Marcus Juby]

Hello there,

I'm building a non-loadbearing strawbale house in the south of Hungary (the 
walls should go up this weekend - weather permitting) and am considering 
making up a cream consistency earth slip, and then mixing this with lots of 
loose straw and 2-3% lime (lime water).  Then I can use this to plaster the 
walls immeadiately as the bales go up.
I'm hoping that if this initial plaster is a couple of centimetres thick it 
will provide fire resistance until I can plaster the walls with more 
attention.  (Which might be in spring)
The earth on site seems ok - I have made some test samples and they stick 
to the bales ok - although I have to add a lot of sand (about 2/3) to stop 
them cracking.
Has anyone had any experience with just earth/straw plaster - would you 
recommend it and if not what would you recommend instead?
Although the earth on my property seems ok - there is also a deposit of 
clay not too far from my house which is used by potters - is there any 
advantage of using a more pure clay - it will result in much more cracking 
won't it?
Any ideas, I'd be grateful.

Cheers,

Marcus