In order to maximise the living space from a towable structure of road-legal dimensions, it was obvious that a folding design would be needed.  A shipping container seemed like a good starting point, but the weight was prohibitive.  However, the format was ideal: shipping containers can be transported by road, sea and rail, and can be towed using a pickup truck and trailer, or mounted on a commercial flat-bed truck. For that reason, it was decided that the design should be based on the dimensions of a "hi-cube" 20ft shipping container, and fitted with the standard corner fittings.

After numerous design iterations, refinements and building a working scale model, the final embodiment emerged.  It incorporates a telescopic central section, lifted by ordinary cable winches, with folding and sliding panels enclosing two floors either side of the central structure, giving a total usable area of around 800 square feet.  The upper floor panels are also raised and lowered using winches, so the only manual labour required is to fold out the gable end panels and raise the upper floor window panels.  Additional panels can be configured to fold out from the walls to provide deck areas and access ramps.  The core of the structure uses a number of bespoke welded brackets to join the structural members, and the gable end panels also use a welded steel construction, but otherwise all components have been designed so that they can be assembled from off-the-shelf materials of standard dimensions.

The kitchen and bathroom are located within the lower area of the central structure, with a raised floor in each to allow for utility components such as batteries, water storage and waste treatment.  Storage tanks are also located in the centre of the upper frame, allowing water to be gravity fed to the sinks and shower.  The remaining area of the upper frame holds two planter beds for growing fruit and vegetables, either hydroponically or in soil.  This rooftop garden is enclosed by clear panels to make a protected greenhouse, which also completes the outline of the pitched roof.

It is envisaged that the bathroom would use a composting toilet, with composted waste subsequently used in the rooftop garden, along with treated greywater from the shower and basin.  The bathroom would also provide a storage area for furniture and fittings when the structure is folded down for transit, as would available space in the kitchen, with any additional contents stowed in the towing vehicle.  The kitchen may incorporate wood-burning stoves for cooking and water heating, with smoke extraction to roof level through an extendable chimney.  A gas stove could be used as a supplement or alternative, perhaps powered by methane from an anaerobic digester, which would also produce compost from food waste.  In another configuration, space in the kitchen counter may be best used to house an atmospheric water generator, which could provide water by condensing it out of the air, with the added benefit of using the cooled air for refrigeration of food and interior air-conditioning.  While such units are commercially available, they are not ideal for this type of off-grid use, so the intent is to design a bespoke atmospheric water generation unit, which would use roof-mounted solar panels to drive the refrigeration circuit and air blowers.