[Strawbale] Load Bearing Multi-storey Straw Bale Tower House Castle

[Chris Mowatt]

Stewart

Thanks for your comments and encouragement. I'm sure that we can build a
straw bale castle. Where there's a will there's a way! Finance is likely to
be our biggest stumbling block, other problems can be worked around. If we
have to use bigger bales(mini-hesstons) we'll use bigger bales. If we have
to use scaffolding, we'll use scaffolding. If we have to build skirts onto
the tower to protect the walls, we'll build skirts. For us, the exciting
process of design is all about starting with the radical and moving towards
the conventional.

> From my armchair, I have often tried to figure out how it would be
possible to
> build the roof of a house first, at ground level, and then, somehow, build
the rest
> of the house underneath it. Straw bale houses, with their forgiving
nature,
> somehow seem appropriate for this sort of thinking. I came up with several
ideas
> - jacking it up; flipping it over onto the built house; rolling it; 'pole
vaulting' it, etc.
> But in the end I concluded that, in fact, there is no real advantage in
doing it at
> all. It's no easier, it's no quicker, it's no cheaper, it's no better. But
it was fun
> scheming, and who knows, maybe I'll try it out one day.
Many buildings are jacked, so the professionals must think there are good
reasons for doing it that way. We need to explore the perceived advantages
and disadvantages and then determine the balance. The idea really excites
me, so I might not be totally unbiased in the weighing up. We're willing to
take risks in this project with everything except human lives, so safety
will probably be the deciding factor.

> I quite agree with you that load bearing structures make more sense in
many
> respects, rather than just in-filling a timber frame. But then timber
frames have
> their place, too. But I would worry about the spreading load in the lower
courses
> of bales. I'm pretty sure that the pressure within them will not be simple
and
> vertical, but will involve spread out sideways, too. A possible problem
with this is
> that if one starts to splay out, the surrounding bales will not have the
rigid,
> interlocking stability to support themselves like bricks (for example)
would. A
> single collapsing bale low down, in a key position like a corner, could
end up
> bringing the whole structure down. Remember that block of flats that
collapsed in
> London(?) in the 70s(?) - a low level structural failure brought them all
down like
> a pack of cards; they don't build towers like that any more.
My feeling is that the inherent flexibilty of straw bales makes for greater
stability. If one area starts to give then the structure moves and the
weight is re-distributed, rather like in a bean bag. However, I am content
to leave this area up to the structural engineers. Although, I think all
professionals need specific guidance on what you want to achieve and how you
want to achieve it, otherwise they will concentrate on the conventional
options.

> 20 metres is one hell of a four story building. Even allowing for a
pitched roof,
> this is still 12+ foot ceiling heights. There is going to be huge weight
bearing
> down on the lower bales, and keeping the all straight, level and even will
be
> absolutely imperative. Building from the top down will mean that you get
to lay
> the least stressed bales first, so your experience, ability and
understanding of the
> structure will increase as you get to the bits where that counts more.
We are thinking in terms of 3.5 metres per floor plus the roof, which may be
as high as 5 metres, giving a total of approximately 19 metres. The girth of
the tower will be 13 to 14 metres. Certainly the build will be a learning
process and we will learn on the least stressed storeys first. We think that
compressing the bales after completion of each course, using the dead load
of the completed sections, will help to stabilise the walls and spread the
loads evenly. If anything we will have a greater problem with the building
the walls for the fourth storey because the dead load of the just the roof
will not be so great.

> Jacking it all up as you go - well of course they build some concrete
tower blocks
> that way, so it's a proven technology, it's certainly spectacular, may be
quicker,
> may be more fun, and who knows, may be more practical. Site insurance,
> including public liability, may be a problem.
I'm looking into this.

> Rendering a storey at a time and then jacking? Things *will* move as you
jack,
> and without the rigidity and structural stability of 'traditional'
materials (ie
> reinforced concrete) cracks are a certainty. You would need a plan to deal
with
> high level repairs, and also for the periodic maintenance that lime or
earth
> renders require.
I'm not convince that things will move. I've spoken to thee heavy-lifting
professionals. They all think it is perfectly practical and low risk. One
might think they had a vested interest in making light of the difficulties
to secure my business, but I made it clear from the start that this was a
low-budget one-off self-build project, not their usual multi million dollar
corporate customer.

> As I said further up, I have absolutely no experience of strawbale
building yet, so
> I've absolutely no business in spoiling your party. If you can deal with
the
> challenges, what a fantastic thing to do.
Absolutely. Thanks for your encouragement.