Hi, we are building single storey extension of approx. 40m2. The soil is clay and there are two thuja trees (10m high) 6m from proposed foundations. We had a building officer visiting today and I missed him unfortunately, so he just spoke to our builder. He requires us to dig 2.5m deep foundations because of these 2 thuja trees. I already questioned that and waiting for his call back. Is this reasonable requirement? Does he have to show me some calculations he based his decision on? This requirement will cost us £4000 more