A lovely large plot in Sydenham with planning for 4 homes, the only problem being that it was over a tunnel. The options for the design could have been to follow the deep truss and piled solution used over the Thames Link Tunnel. A less expensive option was discussed with the client of a balanced raft.
A balanced raft looks to offset the load of the building with the weight of the soil removed. Then the tunnel has no effective load change to it. How does one remove the soil and build the raft without the load affecting the tunnel? The construction requires the old table cloth trick! Croft provided sequence drawings that were followed on site that minimised the unloading of the tunnel to within acceptable limits.
Croft worked through the construction sequences working out the change in loads on the tunnel. Clearly our first run through wouldn’t have been perfect and we undertook iterations of different permutations to find a best fit solution. The final design resulted in the base being cast in 4 quadrants.
Architect: Skyline Design Ltd
Client: Property 1st Ltd