Standard size of bales:
450mm wide x 350mm high x 1-1.1m long (18” x 14”
x 39-43”)
(but occasionally different due to machines)
Average thickness of S/B walls:
approx 500mm wide. Not usual to use s/b for internal walls.
Smallest square S/B possible: about 3m
x 3m
Largest S/B possible: no
limit – depends on design.
Rough cost of bales:
Direct from field – £1.50 each (collect yourself)
Or £2.50 - £3.50 + dep on where and how far. (cost
= diesel to move it)
Where can you get bales?
Straw wholesalers, agricultural merchants
Any questions about Lime :
Building Limes Forum: info@buildinglimesforum.org.uk
Glasite Meeting House, 33 Barony Street, Edinburgh, EH3
6NX
www.buildinglimesforum.org.uk
(no phone number).
What is Cob Building?
Indigenous to the UK, building entirely from clay, sand
aggregate and straw. Usually made from sub-soil on which
house has been built.
Types of Strawbale building:
Loadbearing: Straw walls take weight without the need for
a frame.
Infill: Framework of timber, steel or concrete, straw just
fills the gaps.
Compressive:Like loadbearing, but has a framework, and roof
is lowered onto straw to compress and stabilise it.
What are the healthy alternatives to concrete?
Limecrete – hydraulic lime plus aggregate such as
sand, gravel, blown glass or leca (blown clay). Glass &
leca are also insulants.
How much will it cost to build my house/shed/animal
sanctuary?
Here’s a very rough estimate, using a 2 x 20m wall
as an example.
The sum is based on a straw bale wall using
lime plaster one side.
Straw bale wall 2m x 20m (6 bales
x 20 = 120 bales total)
Bales £360
Hazel pins £30
Lime £2450 (2.5 tonnes + application)
Wall-raising £1600 (7½ days @ £120/day)
Plastering £900 (6 days)
Aftercare £250
TOTAL £4665 for 40m²
= £116.63 per m²
Where are S/B buildings that people can go and look
at?
Clow Beck – Darlington
01327 721778 clowbeckcf@tiscali.co.uk
National Trust Footprint Project Strawbale
classroom – Cumbria
015394 88409 footprint@nationaltrust.org.uk
www.nationaltrust.org.uk
(search for ‘footprint)
Hackney City Farm Educational
Resource Centre-Hackney, London
www.hackneycityfarm.co.uk
Agbrigg Community Allotment building –
Wakefield
jeanrichardson77@hotmail.com
St Dogmaels – 2 storey loadbearing
info@quietearth.org.uk
Yarner trust – Devon
yarnertrust@beeb.net.
www.yarnertrust.co.uk
OTHER QUESTIONS
1.
What about mice and rats ?
2. How long will
it last ?
3. Isn't it a
fire risk ?
4. Is it really
cheap to build ?
5. Can I do it
myself ?
6. What about
temporary buildings ?
7. What else can
be built with straw ?
8.What if some
of my bales get wet ?
9. Is it possible
to repair straw walls ?
10. What if I
want an extra window ?
11. Can I use
straw to add an extension to my house ?
1.
What about mice and rats ?
There
is no greater risk of encouraging mice and rats into your
straw bale house than there is for any other type of building.
Straw is the empty stem of a baled grain crop and unlike hay,
it doesn't contain food to attract furry creatures. Any home
where food is left out in the open is a potential lure for
vermin. Once your strawbale house is plastered, the walls
seem no different to a mouse than other plastered walls. Mice
and rats like to live in spaces between things, as they are
very sociable animals. In barns, they live in the gaps between
bales and in houses they live in cavities and under floors.
If you build straw walls and then clad them in timber, with
an air gap between, this might attract mice: but it's the
gap they like, not particularly the straw. If you build straw
walls, plaster them with clay/lime and maintain them, then
there are no gaps to invite them in, and no cavities in which
they can live.
2.
How long will it last ?
No
one can completely answer this question because the first
straw bale house was built only about 130 years ago. In the
USA there are about a dozen houses nearing 100 years old that
are still inhabited and showing no problems. They have an
increasing stock of houses built since 1980 that are also
surviving with no problems. Here in the UK, we started building
in 1994, and in 1996 in Ireland. As with any other technique
of house building, if your straw bale house is built with
a good design, with quality work and is properly maintained
throughout its life, there is no reason why it should not
last at least 100 years.
3.
Isn't it a fire risk ?
No,
it may seem strange, but when you stack bales up in a wall
and plaster them either side, the density of the bales is
such that there isn't enough air inside the bales for them
to burn. It's like trying to burn a telephone directory -
loose pages will burn easily, but the whole book won't catch
fire. Straw bale walls have passed all the fire tests they
ahve been subjected to in the USA and Canada. Despite the
bales themselves not being a risk, if you plaster any wall
with a half inch of plaster, it gives sufficient fire protection
to satisfy building regulations.
4.
Is it really cheap to build ?
It
depends entirely on your approach to building. If you can
put lots of time into collection recycled materials, or doing
the drawings yourself and keep the design simple, or organise
training workshops to build the walls and plaster them, or
get your friends and family to help, then yet, it can be cheap
to build. For most people, it is more sensible to think of
doing the simple bits yourself (design, foundation, straw
and plaster), and employing others to do the rest (carpentry,
roofing, plumbing and electrics). A small 2-roomed building
might cost about £10,000 (although substantially less
with recycled materials), and a large 3-bedroomed house could
be £40,000. Savings are greater on bigger buildings.
5.
Can I do it myself ?
Yes,
parts of it are quite easy to build. Other parts like roofing
and carpentry are more difficult. It depends on how much time,
determination and dedication you have. But the straw
building technique is simple, straightforward and accessible
to almost everyone.
6.
What about temporary buildings ?
Design
of straw bale buildings is very versatile, and can be adapted
for a more or less durable function. It a building is only
required for a few years, then there may be no need to
build elaborate foundations, or plaster it inside or even
outside.
7.
What else can be built with straw ?
Straw
has been put to many uses. Apart from houses, studios, offices
and community spaces, straw is also used for schools, warehouses,
barns and stables, sounds studios, meditation centres, acoustic
barriers for airports and motorways, food storage and farm
buildings.
8.What
if some of my bales get wet ?
It
depends on where, and how badly. Generally, it a bale gets
wet through the top or bottom into the centre, then it will
not dry out before it starts rotting. So any bales that are
rained on, or stand in water whilst in storage, should be
discarded. This also applies to any bales already in the walls
that are not covered against the rain. But if you have covered
the tops of the bales, and the sides get wet from the rain,
this usually presents no problem, as they will quickly dry
out once the rain stops. The only time this may not be the
case is if the walls are exposed to severe wind and rain at
the same time for prolonged periods, as the wind may drive
the rain into the bale, where it cannot dry until the rain
stops.
9.
Is it possible to repair straw walls ?
It
is not only possible, it's very easy! The hardest part is
making a hole through the straw. This can be done with a claw
on a hammer or crowbar, and by just pulling at the straw.
It can be quite difficult to make the first hole due to the
density of the bale. However, once this is done, wedges of
the bales can be pulled out quite easily. Hazel pins can be
cut throught if necessary, and fresh straw wedges can be packed
tightly back to fill the gap. Experience has shown that if
a section of the wall does get wet, damp remains remarkably
localised. It tends not to spread further through
the straw, and so wedges or flakes of the bale
can be removed and replaced.
10.
What if I want an extra window ?
Again,
it's fairly easy to cut through the walls to create a window-sized
hole. Usually, there is not need to support the rest of the
wall as the wallplate carries most of the load, and the straw
bales act together as an integral material because of the
way they are pinned. Either follow the method above, or you
can use a hayknife, even a chainsaw, although power tools
like this ten to clog up very quickly. Once you've cut the
hole, a structural boxframe can be fixed
into the gap, with the window inside this.
11.
Can I use straw to add an extension to my house ?
Yes,
both loadbearing and framed systems work well here. You may
need to think carefully about settlement, and not make the
final attachments from the straw to the house wall until after
the walls are compressed. You can also easily add an extension
to your straw bale house by cutting a doorway through, in
the same way as described above for making a window. Families
have sometimes encourages their children to build their own
spaces once they've reached a suitable age!
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