My builder has started a single story extension - 6m x 3.5m and we've hit a snag in that building control will not approve the original architect's depth for these of 1.2m and have advised to dig down to 2.6m due to a neighbouring tree.
My builder is telling me that he cannot dig down to 2.6m - due to lack of access for a larger digger - and that the building of raft foundation on the existing depth would be an acceptable solution. However, he tells me that this will cost £6,000 plus VAT on top of the original quoted cost - which equates to an extra 25% of the entire cost of the project.
Can anyone please advise as to whether these extra costs are reasonable?