[Strawbale] Green roofs on strawbale buildings

[Dave Howorth]

On Fri, 2010-09-17 at 11:38 -0400, RT wrote:
> On Thu, 16 Sep 2010 16:37:52 -0400, Dave Howorth <dave at howorth....uk>  
> wrote:
> 
> > On Thu, 2010-09-16 at 15:02 -0400, RT wrote:
> >> Perhaps it would be useful to mention that with load-bearing SB walls,  
> >> it will ultimately be the plaster skins that take the gravity loads.
> >>
> >> As such, it's a matter of detailing the plaster properly to anticipate  
> >> the intended design loading.
> >
> > Would you mind providing a reference for that? I have no trouble
> > believing that the stiff plaster takes dynamic loads, but I don't see
> > why it would take the static loads, given precompressed bales and all
> > static loads applied before the plaster is applied. So experimental
> > evidence would be very valuable.
> 
> Dave;
> 
> Just curious as to how you think a SB wall assembly differentiates between  
> the dead and live components of the gravity loads to which it must respond  
> and then proceeds to direct the straw portion of the wall to deal with  
> only the dead load component of the applied loads ?.

I don't think it does, so no question to answer.

> (And I don't think it's reasonable to assume that all of the dead loads  
> will be in place at the time of plastering. ie think of multiple storey  
> structures as a "for instance")

It doesn't matter whether there are some cases where the conditions I
stated don't apply. I'm specifically interested in the cases where they
*do* apply, since I believe they occur in a significant fraction of
loadbearing construction.

> To anyone who has any doubts about the harder/stiffer elements taking the  
> loads I would suggest a simple demonstration they can do on their own to  
> confirm:
> 
> Find a piece of deep pile broadloom or carpet and place a few small stones  
> into the carpet in a manner that the carpet strands stand proud of the  
> small stones.
> 
> Then place a chair or ladder next to the piece of carpet, take off your  
> shoes and socks and climb up and then jump onto the stone-studded carpet.
> 
> When you recover, comment as to which element (hard stone (analagous to  
> the plaster in a SB wall assembly) or the compressible carpet (analagous  
> to the straw) took the load .

I'm not sure why you mention the experiment above, since it deals with
dynamic loads and a completely different situation. It seems completely
irrelevant and possibly misleading to me.

> As to official in-lab test data, any of the compression resistance tests  
> done on plastered wall panels (in North America, Europe, AUS or NZ) will  
> provide the same "evidence".

So no specific reference you can recommend then? I really would
appreciate one because in all the ones I remember they plaster the bales
first and then apply the load, which is not the situation in which I'm
interested. Perhaps I've misremembered one or more, or perhaps I'm not
aware of some, which is why I would like a specific reference, if you
can provide one.

> Those same tests will also show the importance of proper detailing of the  
> plaster to deal with the expected failure modes (ie Euler buckling,  
> localised crushing, delamination etc.)

Indeed, the detailing is important for many reasons.

Cheers, Dave