Building an early cost plan for five support buildings

We supported a modular building contractor developing early cost plans for five support buildings within a major leisure development. The combined working estimate was approximately £8 million. We turned developing design information into elemental cost plans, with quantities, rate sources and stated allowances showing how each estimate had been assembled.

Background

The buildings served different operational functions and varied in size and layout. Their design was sufficiently developed to identify the principal elements, but many construction details and specialist requirements remained to be confirmed.

The client needed more than a single cost-per-square-metre benchmark. It required a working estimate that could explain the effect of the emerging design and be revisited as the information became more detailed.

Our approach

We structured each building into a consistent set of cost elements covering substructure, frame, roof, envelope, internal construction, finishes, fittings and services. The detailed schedules sat behind individual summaries, allowing a reader to move from the overall figure to the quantities and assumptions supporting it.

The rate build-ups drew on available project cost information and recognised published cost data, with the source or adopted basis recorded in comments. Historic rates were adjusted to the estimate’s pricing date where appropriate, keeping the time basis of the information visible.

We considered the content of each allowance rather than applying one broad rate to the whole building. For the steel frame, for example, the pricing basis identified fabrication and erection alongside further allowances for associated connections, protection, design and warranties. The envelope descriptions similarly explained the assumed system and the supporting components.

Roof and canopy geometry required separate attention. Decking, waterproofing, insulation, parapets and soffits did not all share the same area or pricing basis. Breaking those components out helped the estimate reflect the form of the building rather than relying solely on its floor area.

Services were developed across their principal systems, including water and drainage, heating and cooling, ventilation, electrical installations and controls. Testing, commissioning and builders’ work in connection with services were identified within the cost structure so that those supporting activities remained visible.

Where there was no firm cost information, we used a stated notional allowance. This included some architectural features and smaller specialist items. Exclusions were also recorded, including work assumed to be complete before the contractor’s involvement and external works outside the measured building scope.

The summaries then brought the building costs together with separate allowances for preliminaries, overheads and profit, and design risk. Keeping those additions visible allowed the client to understand how the direct construction estimate related to the overall figure being put forward.

Outcome

The client received five detailed cost plans with a consistent elemental structure and an identifiable pricing basis. They provided a working foundation for budget discussions and further refinement as design and specialist information became available.

Our contribution was to make the early estimate explainable. The client could see which costs followed from measured design information, which relied on benchmark rates and where a provisional assumption still needed to be tested.