There is something
downright joyful about strawbale homes, with a humble beauty that is
beyond skin deep.
With the introduction of the Homestead Act of 1862, "sod-busters" were
obligated to develop and reside on their new
property for five years in order to ensure ownership. This created a
demand for a fast and affordable means of house construction. Initially
strawbale houses were seen
as make-shift structures to provide temporary lodging until funds
became available to pay for the construction of a "real
house". However, strawbale houses quickly proved to be
comfortable, durable, as well as affordable, and so came to be regarded
permanent housing over time. Indeed, over the past century they have
often outlived neighboring timber-frame houses and a number
today are beginning their second century.
After the second World War ended, some veterans
turned to strawbale
construction as an economical means of building their starter homes.
However, modern strawbale construction didn't emerge until the late
1970s when the energy crisis created by the oil embargo helped
bring issues of sustainability to the public consciousness. Now,
are being built around the world, including northern Canada, Mongolia,
Russia, Mexico, Australia and New Zealand.
Strawbale construction's growing popularity stems from a number of
- it utilizes an
inexpensive and renewable "agricultural waste
- it requires a relatively
simple construction technique which is easy for beginners to learn,
- it involves few synthetic
- it provides effective
For these reasons it's growing in popularity,
especially with do-it-yourselfers, "owner-designer-builders", and other
proponents of sustainability.
Strawbale buildings can be constructed from many different plant
fibers, not just
grass-family species such as wheat, rye, barley, blue-grass and rice,
also flax, hemp, etc. Recycled materials including paper, crushed
plastics, whole tires, pasteboard,
waxed cardboard, crushed plastics, whole tires, and used
carpeting have also all been used for
A recent innovation is the use of high-density recompressed bales or
"strawblocks. This method provides higher compression strength.
Standard concrete footing/foundations or thickened edge-slab-on-grade
foundations have been typical. Bales can also be stacked over stem
walls with joisted floors. With load-bearing strawbale homes rubble
trench foundations or Earthbag construction foundations are
increasingly used, as an alternative to conventional footings. Some
pioneer designers are even using rock-filled gabions or earth-filled
"bastions" in lieu of concrete. Strawbales have been used to insulate
the floor from the slab, or to provide subgrade perimeter insulation,
but this must be done with care, due to the importance of isolating the
bales from undue moisture. (Moisture levels higher than 18% support
mold growth in both straw and wood.)
The original "Nebraska" strawbale building method utilizes
the strawbale walls as the support for the
A newer method of construction utilizes a post and beam framing
system to carry roof, wind and seismic loads. Once that structure is
in place, the walls are then infilled with strawbales for insulation.
This type of structure is popular today because it allows bale
be accomplished with the roof already in place, or "in the dry", and
more readily be demonstrated to conform to building codes.
In some cases, both methods can be used,
with load-bearing perimeter walls and pole or stick-frame support at
the interior or ridge.
Strawbale buildings can employ many different types of roofing designs.
Sometimes a barrel-vaulted roof is used, but most often a conventional
roof structure is attached to a
load-distributing plate or beam at the top of the straw walls. These
conventional roof structures are typically insulated with strawbales
which then provide high insulative and acoustic benefits. Additional
insulation options include soy-based
foam, rice-hulls, wool or
cotton batts, and even recycled cellulose.
and Interior Finishes
Typically strawbale walls have stucco exteriors and
plaster interiors. The combination of straw-bale/stucco behaves
like a sandwich panel, with the rigid stucco skins bearing
much of the load in addition to adding considerable overall wall
for straw-bale walls is most commonly a mix of cement and sand.
mixtures containing earth or clay and/or a high percentage of lime in
place of the cement are increasingly popular. This alternative
increases water vapor
permeability through the walls.
Strawbale walls are typically 21 to 26 inches wide when stuccoed and
plastered. This thicker than average wall results in deeper window and
similar to those found in stone and adobe buildings. Since bales can be
shaped easily, they can be used to produce curved designs. When
used in combination with plaster, they can create an imperfect texture
and shape which some people find appealing. Flat straight walls can be
achieved by the
application of more plaster.
Straw-bale buildings offer high insulation value.
The typical interior finish of a straw-bale wall is either cement or
gypsum plaster, or a combination. This results in excellent
thermal mass on a diurnal cycle.
A strawbale home's thermal mass minimizes the thermal swings due to
daytime warming and
night time cooling, by first absorbing and then gradually releasing
This can reduce the need for fuel or
electricity to regulate temperature.
Strawbale building utilizes locally available materials, and basic
construction techniques that require little specialized or proprietary
materials and equipment. It has often been successfully used by
inexperienced builders working on their own homes.
Since straw is an abundant agricultural waste product it is, therefore,
relatively cheap for a building construction material. In bulk,
are usually sold for approximately the cost of baling and delivery.
Farmers will occasionally sell bales for under cost in order to clear
storage sheds prior to a harvest.
In most regions, straw is baled only once each year, and so must kept
dry and stored for use at other times of the year.
Strawbale walls are thick and dense enough to keep out most pests. In
addition, the plaster exterior makes them unattractive and
impenetrable to animals and insects. Finally, because straw contains
minimal nutritional value, it does not attract
While loose straw is highly flammable, after being packed into a bale
too dense to allow sufficient air in for combustion. Think of it this
way, it is far easier to
light a single sheet of paper on fire, but next to impossible to burn a
closed telephone book. In construction it is critical to have,
at a minimum, a parge coat of plaster on all surfaces of the wall.
Application involves troweling on a thin coating of mortar
and then brushing it smooth.
Failure to add the parge coating can create a fire hazard. A spark from
an electrical short
can ignite the hair-like fuzz of an exposed
bale. The flame spreads upward and sets the wood framing on fire
causing it to burn. The typical fire will result in little
fire damage to bales, but extensive water damage due to the fire
There are limits to
strawbale's structural strength. Load-bearing
strawbale walls are typically used only in single-storey
or occasionally double-storey structures. A basement foundation
Strawbale design and
Straw-bale construction is still considered an experimental
construction method in many
jurisdictions. This means that:
- local building codes may
not cover it,
- local authorities may
not recognize it, and
- most contractors will not
in its use.
- It is important that
strawbale buildings be designed to eliminate the
possibility of moisture entering the walls, especially from above. For
this reason, designs usually incorporate roof shapes and overhangs
are wider than
normal to minimize the risk of water entering the walls.
- Finally, because
strawbale walls are significantly thicker than normal walls, the
amount of actual living space within the walls can be significantly
smaller than the footprint of the building.
resources on strawbale construction.
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