A cautionary tale, make sure when digging out for a raft the ground worker/digger driver understands the arrangement:
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Gave the GW's a plan, section and details for the raft and left them to it, went back 2 weeks later to catch up and they had dug the whole site out a meter deep, we then had to spend a couple of weeks using salvaged scaffold boards shuttering it all up and back filling to get back close to square 1, and it still took 7 * 8 yard concrete lorries to pour the raft, over engineered to say the least.