The project comprised the extension and modifications of an existing two storey doctor’s surgery to a four storey medical centre, incorporating a dental surgery together with a new build two storey rear extension.
Initially we acted as a consultant to the client, carrying out targeted site investigations and considering feasibility options for the existing two storey 1980’s building. Our remit was extended to enable production of a working scheme up to RIBA stage D. This followed with a Novation by the client to the contractor to produce calculations and drawings for B.Regs approval and for construction. At the early stages of the project and on the basis of limited information, we carried out a feasibility study to determine how many storeys could be safely added to the building. The outcome suggested that the effect of adding two floors on the two existing, would add a significant load to the existing shallow piled foundations, thus reducing their safety factor below what would be acceptable by Building Control and building insurance companies.
The client explained his business case and the reasons why a two storey extension was vital for the viability of the project. Thus we were tasked with finding a cost effective way of utilising but not overloading the existing substructures. During internal technical reviews of the project, the most obvious option, installation of additional foundations, was dismissed as this would increase the duration of the works and cost considerably. This was unacceptable to the client as we knew that he relied on maximising his rental income both before and after the completion of the works. We thus decided to investigate the ground conditions further and suggest to the architect and client to consider different forms of construction.
We investigated the ground conditions immediately beneath the ground beams and found that these were cast directly onto the ground. This, coupled with the age of the property, gave us the opportunity to direct a limited amount of the surplus load through the ground beams and directly into the ground. This on its own was not adequate to solve the problem. However, following discussions with the architect and client, it was agreed to construct the extension in lightweight materials for the new floors walls and roof (thin gauge, pressed metal framing and render on board). The combined result (additional foundation capacity and reduced building weight) negated the need for expensive and disruptive foundations and enabled the project to proceed within the anticipated budget. The Stage E (detailed design) calculations substantiated our early assumptions and scheme calculations.
Client: Tower Asset Management Limited
Contract Value: £1.8m
Structural Engineer: Ellis and Moore