We have recently built an extension in a large family house in Clapham. We enocountered two problems when we started the build. Firstly a hired company who cut a tree down for the family covered over some root remains they failed to remove with soil. Unfortunately this lay in the foundation trench which we had to dig out by hand then dig a bigger trench in its place. This created the problem that the calculation for the foundation no longer worked so our engineer recommended a more highly reinforced concrete foundation.
Secondly we found that a steel beam calculation was done incorrectly by the family’s architect. The beam was not wide enough thus our engineer modified the plans to add a wider platewide to support the wall so that three stories of building could rest on it.
In the end we delivered a beautiful addition to the home and overcame problems that did not affect your delivery timeframe.