Why build with sandbags?
Sandbag building provides for low carbon footprint thermally efficient building. These structures feel warm in winter and are cool in summer.
What is the square metre cost to build with sandbags?
There is no such thing as a standard building rate per square metre. No two structures are the same and therefore no two building rates are the same. This does not relate to the finishes in a building as finishes on average make up between 20 - 30% of the total building cost.
Cost is always dependent on the specification and the location of the build. Sloping land will increase building cost. The type of soil condition will influence the type of foundations that are required.
Take two buildings for example - the one measures 10m x 10m and the other measures 20m x 5m. They are both 100m² - but clearly the second building is going to cost more. Other influencing factors are going to be the wall height of the structure as well as the window and roof specification. Of course, the other factor is the size of the structure. The bigger the size - the less the cost per square metre.
For the purpose of an estimation, let us assume a level piece of land - standard foundation and straight forward roof and window specification. A single storey three bedroomed house measuring 180m² in this situation will cost approximately R4,000 m².
What does this cost include?
Structurally engineered foundation, fully insulated roof, ceilings, cornices, plastered walls, windows, door frames, doors, ironmongery, electrical and plumbing.
How big are the sandbags?
Once filled they are 290mm long x 235mm wide x 85mm in height. A total of 42 bags will be required per sq/m.
How much do these bags cost?
Their delivered cost in South Africa is R 1.60 each. Assuming a cost of R 200 per m³ of sand for the bag infill along with the cost of the bag means that this is about 40% cheaper than the cost of bricks over the same area.
How much sand is needed to fill a bag?
Depending on the density of the sand being used, each bag will contain about 9kgs of sand.
What type of sand can we use?
Fill sand or river sand is preferable. But whatever sand should be suitable as long as it has a low clay content and no organics are present within the soil.
Apart from the sand, is anything else placed in the bag?
Nothing other than sand is placed within the bag.
Apart from the bags, is there anything else needed to effect this build?
A non-structural framework is also required. The bags are placed within this framework.
What is the measurement of the completed wall?
The external plastered wall measurements are 270mm - while the internal wall measurements are 200mm.
What is the weight of a sandbag wall?
On average a sandbag wall is 40% heavier than a brick wall (depending on the density of the sand being used)
Is this method of construction fast?
Building an external wall with bricks only achieves a building rate of 6.16m² (assuming that a bricklayer is able to lay 700 bricks per day). By contrast, 20m² of vertical walling can be completed per day using a crew of two operators - making it three times faster.
How do we secure cupboards and shelving onto these sandbag walls?
Shelves, cupboards, TV's and brackets are secured in the normal manner, however special fasteners are used. In cases where exceptionally heavy equipment is going to be installed, a simple concrete beam is created on top of the bags in the area concerned.
Can we build a double storey with this method of construction?
Yes, providing that supportive concrete columns are placed strategically throughout.
What type of windows are used with this method of construction?
Any type of window can be incorporated into sandbag construction.
What type of roof can be used for this method of construction?
Any type of roofing material can be secured onto the sandbag walls.
Is this method of construction approved?
Yes, this method of construction has been approved by the Agrément Board and the NHBRC.
Are there any restrictions in terms of design?
No, the boundaries are set by your own imagination.
How long will a house like this last?
Since a sandbag house is not subject to rising damp issues, one can expect this type of house to outlast a conventionally built house. There are numerous cases in Europe where sandbag structures are over 100 years old. There are several sandbag structures in the Western Cape area that are almost twenty years old - and still look as good as they day they were built.
What type of foundations are recommended for this building system?
The type of foundation required is determined by the appointed structural engineer, however, a conventional raft foundation would be most suitable.
Will banks provide finance to build these houses?
Banks are currently assessing this building system with view to providing bonds. This process is expected to be completed before June 2016.