A House of Straw

The house looks like any other, four walls, roof, windows and doors. However one thing sets it apart from the rest. Built in 2005, this modest house in Kalagedihena, Gamapaha was built using compressed straw bales instead of bricks as an experiment by Engineer Piyal Ganepola and Engineer/Researcher Shozo Inagami.

By Udeshi Amarasinghe | Photography by Piyal Ganepola

With the aim of introducing technologies to Sri Lanka that are sustainable and would not harm the environment, Engineer Ganepola and Engineer Inagami focused their research on a technology that fulfilled economic, environmental and socio-cultural sustainability parametres.

“Straw is a waste material and it is disposed of by burning which emits toxic gases that are harmful to the environment”, explained Eng Ganepola. Additionally the use of straw also negates the harmful effects on the environment through burning bricks in kilns and the use of fuel. Currently straw is used as a fertiliser, according to Eng Ganepola, farmers can use excess straw from one harvest to build a house for themselves at a minimum cost.

Straw bale technology has strong potential, as it can be adapted to Sri Lanka for low cost applications. This straw bale brick is made using a machine, which has been fabricated locally. The straw is compressed using this machine to produce bales that have no oxygen inside. Each bale is approximately 25 Kg each. As the bale does not contain oxygen, it is fire proof. Furthermore the external walls are plastered. Eng Ganepola affirmed that the straw bales were tested and all codes in terms of fire safety have been fulfilled when building the house.

Eng Ganepola explained that straw bale is a very good structural material as it is strong and durable in the absence of moisture. “Straw will decay only if there is water if not it can survive for any period of time. May be for centuries also. There are buildings that are older than 20-30 years in North America” described Eng Ganepola. The model has stood firm for four years without any problems. However the researchers are yet to affirm the adaptability of this technology to Sri Lanka because the climate is more humid.

Though straw bale buildings are new to Sri Lanka this technology is widely used in Australia, Canada, Europe, North America, China and Iraq. The only difference is the humidity levels. As Eng Ganepola explained straw has good thermal properties. In Australia during winter heaters are not required because it remains warm inside the house, whilst during the summer, the building is very cool. In Iraq this technology has been used to build small houses for Internally Displaced People.

The model house in Kalagedihena is a single storey house of a basic architectural design. The house consists of a hall, pantry and bathroom. As this house is a load bearing structure, the entire wall is built using straw bales. However the bathroom is built using red bricks, as there is the chance of water seeping through. On the experience gained from the model house Eng Ganepola and Eng Inagami commenced on the construction of a two-storey house using straw bales. However the structure is in concrete whilst the in fillings of the walls are straw bales. The strength of the straw bale brick has been tested and it can take the weight of a normal roof. However if the house is to be more than one storey then the structure needs be in concrete and intermittent columns are a must.

Considering the strength of straw bale walls, the width of the wall is approximately 1 ½ feet, according to Eng Ganepola. According to a research done by the Open University a 1 foot wide wall is sufficient to take the load of an ordinary house. The only disadvantage is that straw bale houses require fairly wide walls, which would consume more space. Straw bale houses can be built on any type of land as long is it is not flood prone.

Eng Ganepola explained that these straw bales could be used to build houses with elaborate designs such as arches as evident from the building constructed in countries such as Australia and Canada etc. The technology has high and low cost applications which is also evident from the structures built abroad. An example he showed was a house built in Mexico constructed using bamboo sticks to reinforce the structure. However as the houses built in Sri Lanka were not commercial endeavours the straw bale structure was reinforced with iron rods, which is a more high-end construction.

The advantage for Sri Lanka is the availability of straw, cost effectiveness of the technology, quick construction and being environmentally friendly. The research is funded by Eng Inagami and his aim is to eventually introduce straw bale technology to Japan. Eng Ganepola is confident of the success of straw bale technology in Sri Lanka and he himself is constructing his retirement home using this technology.

Principle Architect/ Engineer : inagami Shozo

Other Consultants:

Project Manager: Piyal Ganepola

Structural Engineers : Inagami Shozo / Eric Ediriwickrama

Area of the Site : 400 Sq ft

Date of Completion: Feb 2005

Project period: 1 year including research

Contractor : Marlin Enterprises

Client: Saman Perera