- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 31 Jul 2018
Straw bale construction
Straw bale construction is a method of building that uses bales (or bundles) of straw. Straw bales can be used as structural elements, insulation or both together. The use of straw bales is typically found in 'natural' building projects, or earthen construction, and while historically it has been a common form of building material in many parts of the world, it has been received increased attention more recently due to its sustainable properties.
Two different types of straw bale are in common use:
- Bales bound together with two strings.
- Bales bound together with three strings (these are larger in all three dimensions).
 Construction techniques
The techniques used for straw bale construction usually involve stacking rows of bales on a raised footing or foundation. A capillary break or moisture barrier is inserted between the supporting platform and the bales. Pins made of bamboo or timber can be used to tie bale walls together, or surface wire mesh can be used.
The bale wall is then stuccoed or plastered using either a lime-based formulation or earth/clay render, although these should be considered with regard to the local climate conditions. For example, in wet climates, a vapour-permeable finish may be preferred to a cement-based stucco.
Straw bales can be designed to provide load-bearing structural support to a building, as well as to provide lateral and shear resistance to wind and seismic loads. They can also be designed to serve as an insulation substrate, with a separate, load-bearing structural frame, typically made from timber. By building a skeletal framework first, a basic roof structure can be provided which protects the bale wall during construction, which is when it may be at risk of water damage.
 Advantages and disadvantages
Some of the advantages of straw bale construction include:
- Straw bales are made from a low-cost product.
- Insulation values of R-30 - R-35 can be achieved.
- The thickness of straw bale walls can help reflect sunlight into a room, and provide space for window seats.
- They are relatively easy and cost-efficient to install.
- Straw bales have a low-embodied energy.
- With good maintenance, straw bale construction is very durable.
- Straw bales are 100% biodegradable.
- Properly-constructed straw bale walls can offer better fire resistance than conventional timber frame construction.
Some of the disadvantages of straw bale construction include:
- Moisture and mould are significant risks. Straw must be kept dry to avoid compressed straw expanding due to moisture absorption, which can lead to cracking.
- Fire is also a considerable risk, however, because of the density of bales, fire tends to smoulder rather than spread when an ignition source is removed.
- As it is not a conventional building material, building regulations can present obstacles to its use.
- Wall thicknesses mean that more of the building’s overall floor space is unusable.
- Unless straw bales can be sourced from near the construction site, the cost of transporting them can be high.
- Care must be taken to keep rodents and other small animals from infiltrating straw bales during construction.
- Straw dust can cause breathing difficulties for people with allergies.
In 2014-15, the University of Bath undertook research into straw bale construction. They focused on ’ModCell’ panels, which are prefabricated panels consisting of a timber frame infilled with bales and with a breathable lime-based render. They found that straw bale construction provided for healthier living through higher levels of thermal insulation and humidity regulation.
As a result of this, the first straw houses to be offered on the open market went on sale in 2015. The seven houses, located in Bristol, were built-clad but with timber-framed straw bale walls. The purchase price was below average, and it was estimated that fuel bills would be up to 90% cheaper than an equivalent brick-built house.
Peter Walker, from the University of Bath, said:
”In terms of durability, we have undertaken laboratory tests and undertaken monitoring of existing buildings and we have also done accelerated weather tests. The results of all these tests suggest that straw is a very durable construction solution.”
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
A masterplan is a framework within which a location is encouraged to develop or change. Read our introductory article.
New consultation announced on a specialist Housing Court to settle landlord-tenant disputes.
ICE responds to a transport consultation advising the government to make decisions enabling more inclusive cities.
BRE and Loughborough University complete first phase refurbishment of demonstration home.
How the risk of collapse of fibrous plaster ceilings is being addressed in theatres.
If you’re a great writer and have practical experience of the construction industry, it could be you.
Frustrated by long documents or technical jargon? Put off by sign-up forms or costs? Take this 5 min survey to help improve construction knowledge.
These are attached to land that is the subject of a planning permission, and used to compensate for negative impacts.
ICE Scotland launch its new report for a long-term, holistic approach to infrastructure planning and funding.
Building surveys provide a detailed evaluation of a property's condition and involve an extensive inspection.
Government announces additional £2m funding for councils to tackle rogue landlords.