how can we Support neighbouring patio and sun lounge as our footings are deeper

[Lk1980]

Hello Everyone,

I was hoping someone could advise. We have a semi detached property and my neighbour has a patio and sun lounge. We are building an extension but due the trees in her garden (which are less than 3 meters) structural engineers have asked to go for step footings (1.2, 1.7 & 2.1 meters respectively)

 

The builder said once they start excavating (especially where footings are deep) there is a very miniscule chance of land slide depending on the quality of the land beneath neighbour's patio.

 

I have asked him to ensure his insurance is sufficient to cover the damage if it happens. Also, I was wondering if anyone can suggest ways we can ask builders to provide support whilst construction is underway to support the neighbouring patio and the sun lounge whilst we put the footings in place or build a retaining wall. Drawings attached.

drawings with calc.pdf