Building with Straw

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Building with Straw

• Straw bale, Cob, and Light Clay Construction

Alison Ray 20 September 2004
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An experience with straw Bioconstruindo 2004
Heidi Queen of the Strawbale Pile
Brazilian Cerrado, Rippin the Curl
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Bioconstruindo bamboo geodesic dome, vigas
reciprocas ferrocement caixa de agua
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Quick History of Straw Bale Homes

• 1800s Nebraska Settlers
• Lumber expensive and sod too precious but straw
  was extremely abundant!
• Invention of horse-powered baler in mid-1800s and
  later steam-powered made home construction faster
  and more efficient
• Warm in winter and cool in summer, not just a
  temporary thing

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Constructing a Straw Bale Space

• Straw bales are stacked like blocks to form the
  walls of a structure
• Load-bearing walls
• Infill for post and beam
• Straw bale walls are highly insulative (up to
  R40), sound proof, and when plastered resistant
  to fire, vermin, and decay
• Works great in combination with cob

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Laying and sewing the bales
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Binding the bales with wet cob
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Nearing the top
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Natural plastering cob and clay
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Almost done
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Quick History of Cob

• Cob is an old Devon word for mud wall
• Cob has been Devons traditional construction
  material since 14th century.
• Traditionally, straw and dung, were added to the
  clay sub-soil to reduce cracking
• Cob can last for many years so long as it does
  not accumulate moisture
• Some houses in England are 600 years old and
  still standing

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Cob Construction

• Cob is a mixture of clay and sand (earth), straw,
  and water
• Cob walls have no structural elements
• Natural plaster or rendering must be applied to
  prevent moisture
• Cob is favored for its freeform quality

Our cob bird-bench
Mixing the clay, sand and water takes muscles!
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Advantages of Cob

• Abundant, inexpensive and replenishable material
• Free-form, creative and artistic
• Easy to do (and fun!)
• Structurally more stable than conventional homes
  to earth quake
• Cob is a flexible material that moves with the
  Earths movements while staying together
  (allowing for rounded, natural shapes
• Provides thermal mass, storing suns energy and
  releasing it at night but also cool and shaded in
  the day

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Cob socials! Fun to dance and play with the
earth while creating functional art!
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Inserting a window into a cob wall
Forming cob bricks from the wet material
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Cob wall with tree stump decoration
Cob Giant (oven and bench)
Yes, its the same picture, but look at the cob
this time!
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Taipa Leve Light Clay

• German tradition for over 400 years
• Leichtlehm or Wattle and Daub
• Timber provides most of the load-bearing
  structure
• straw, earth, woodchips, sawdust or any material
  provide insulation and infill
• Panels created to be independent so houses could
  be easily deconstructed and transported

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Using Light Clay Construction

• Loose straw or other material is coated in a clay
  slip then tamped into temporary forms for infill
  of a wood frame
• The material will dry about 1 per week, an
  applied plaster prevents moisture from entering
  the wall
• Panels are light weight, insulative, non load
  bearing and great sound proofing
• This technique can also make sawable construction
  blocks

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Creating light clay walls
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Tamping down the walls
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Building the Walls
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Natural Building is good for the environment, for
human health, and community-building, but most of
allits fun!!