[Strawbale]Rendering the outside only

[Duncan Lithgow]

Stewart Hargrave wrote:

>I've been helping a musician build a strawbale recording studio (the 'Strawdio'). It 
>is a simple, one storey, load bearing structure - four walls and, soon, a green 
>roof. 
>
>He has been wondering about the possibility of leaving the inside surface of the 
>bales bare. This would be accoustically superior to a rendered or plastered 
>surface, and would be ideal for it's intended use. But I wonder if anyone would 
>like to comment about the implications of doing this - structurally, thermally, or in 
>any other way?
>
>He's been keeping a journal about the build; you can see it here: 
>http://www.pindropclub.co.uk/strawdio/journal.htm
>
>  
>
I refer to 'Serious straw bale' (Lacinski and Bergeron, A Real Goods 
Solar Living Book) and especially the article about the Sivananda Lodge, 
look at page 206.

The strongest, or at least most rigid part of a strawbale construction 
is the bond between the surface render (plaster/ clay etc) and the 
surface of the bale. This network of straw going in all directions set 
rigidly into a firm render is like a thin but continuous adobe brick - 
which I believe is just a mix of clay/ lime/ straw.

So that's the structural bit, now on fire. Never ever ever leave any 
strawbale surface unplastered. The fire risk is too high. In theory you 
could have packed everything so well and tight that only the surface 
would burn, but in practice that's unlikely. Small gaps between some of 
the bales is all you need to get smouldering fires inside the wall. Your 
structure is then slowly burning down around you. And in a music studio 
with lots of electrics and maybe the odd smoker - it's asking for 
trouble in my opinion.

Take all of what I say with salt - I'm a reader on strawbales with 
minimal real-world experience.

Duncan