Start with a home that is specified
The Switch House reference design supplies a concrete benchmark: a family home with a defined structure, layout and thermal specification. Its bill of materials identifies the components and the work involved.
That gives procurement a basis for comparison. Suppliers price identifiable quantities and builders show how their offer meets the same performance requirements. The reference home makes the cost discussion specific.
Keep the cost layers visible
Materials and workshop production sit at the first layer. Site labour and fit-out complete the building work. A contractor then carries responsibility for delivery and charges for preliminaries, overheads and profit.
Professional fees, programme costs and construction-period finance add further layers before the home earns rent. Site infrastructure has its own funding route. Combining these categories without showing them hides the true funding requirement.
Use the benchmark to control the tender
The materials estimate gives the Trust a floor against which to judge a bid. It does not establish a guaranteed construction price. The contractor’s tender, the site conditions and the full programme budget determine the delivered figure.
The Trust’s reference specification also includes choices beyond the standard template, including its heat-pump requirement. Those choices must remain visible in the model. A credible affordability claim follows the complete cost chain from component to occupied home.