Our design for the Self Build on a Shoestring competition made it to the last 16!
As this building effectively does not have foundations, but instead sits on a raft bedded on stabilised ground, there is a very low amount of site preparation needed. An area 1m wider than the building footprint is stripped of its top soil. This top soil is spread over the rest of the site.
The foundations are the truly innovative aspect of this design as the building rests on a steel raft which sits on stabilised ground. We have used this concept for a visitor centre in a woodland setting, where the building sits on an oak raft. Concrete rafts are also fairly common. Essentially excavation is 1/5 that of standard concrete foundations and the quantity of materials and labour required is greatly reduced. The equivalent concrete foundations for this project would cost 3 times as much.
For the external walls an environmentally friendly material takes precedence over the cheapest option. Hemp-lime is a great material for mediating between internal and external conditions. It creates an airtight but vapour permeable envelope which both eliminates the risk of internal condensation and provides a great thermal mass. It is also possible for unskilled workmen, including the self builder themselves to apply the hemplime under supervision with minimal training.
Self Build on a Shoestring 2013' was organised by the National Self Build Association (NaCSBA) and the judges included TV presenters Kevin McCloud and Charlie Luxton. The competition was sponsored by the Grand Designs Live exhibition, and the top 16 entries were displayed at the NEC, Birmingham on the 5th/6th October.