With the geometric design of the structure completed, it was time to refine material selections for compatibility and strength. Fluid simulation software was used to determine the forces on the various aspects of the structure at different wind speeds. The predicted forces were then superimposed onto the structure in mechanical simulation software to calculate component deflections and stresses. Loads on the interior of the house, simulating furniture and people, were also modelled in the software - both separately and in conjunction with the wind loads. With the materials listed below, it was calculated that the structure would withstand a wind speed of 60mph (100km/h) with a good factor of safety, though practical testing at this and higher wind speeds would be needed to provide an assurance of safety.
Ultimately, structural timber offered the best combination of strength, workability and cost, with the advantage of being a sustainable building material. Aluminium was chosen for the roof frames in order to reduce the weight of the upper structure while maintaining stiffness, and was also used for the four swing arms that raise the roof panels. Mild steel was selected for all brackets, offering high strength and good workability at low cost, and stainless steel was chosen for the gable end panels on account of being easy to fabricate and offering good corrosion resistance. An easy-assembly aluminium tube system was chosen for all window frames and the greenhouse roof panels. The remainder of the material selections included polycarbonate for windows, fibreglass for roof and wall panels, bamboo for the downstairs flooring, wood-framed plywood for the upper floor (which could later be covered or carpeted), and rigid PIR insulation sheets throughout.
After two years of design work, it was time to build the first prototype. It took three months to assemble the structure to the point of completeness depicted in the photos and videos. At this stage, it still needs window panes and solid end panels installed to make it weatherproof (along with rubber seals between sliding/folding components), as well as the greenhouse roof frames to be finished and filler panels to be added around the top floor end windows. On the interior, there are still the bamboo floorboards to attach downstairs, the upper floor panels to be finished and covered, as well as insulation to be installed throughout. I had a break scheduled to spend time with family, so the goal was to get the structure to a point that demonstrated the successful mechanical operation of the design, which has been achieved.
The prototype build budget was £15,000 (US$18,000), though the final cost will be slightly higher- around £18,000 (US$22,000) when the shell of the structure is complete. Based on learnings from the prototype build, it is envisaged that the cost price (materials only) could be brought down in line with the original budget.