Proposed Foundation Depth – Investigations and Serving Notice

Question

We are the leaseholders of a 2 story maisonette in a terraced property composed of 4 storeys. The freeholder is the Local Borough.
 
We are planning to do some work (demolition of an internal partition wall on the lower ground floor) and the structural engineer suggested to put in a beam to bear the load of the above floor and potential walls upstairs. He mentioned that the builders should excavate for 1 metre to strength the foundations. Of course this will happen within 3 metres of the adjoining properties.
 
We have 2 questions:

1. How do we find out the depth of the foundation level of the neighbour property?
2. Do we need to give the notice of the work even if it is likely that the excavation will not go at a deeper level than the neighbour foundations?

Answer

You could expose a small part of the foundation on your side by digging a trial pit. If that is not possible you will have to make an educated guess considering the type and age of the properties.

If you do not excavate deeper than the base of the foundations you are not required to serve notice.

If it turns out that you will be excavating deeper than the foundations you will need to serve notice to the neighbouring Freeholders and any long leaseholders that have an interest in the wall. You would also have to serve on you own Freeholder and the leaseholders of any maisonettes above you. It is also likely that you will need a license to alter from your Freeholder for structural alterations to you maisonette (check your lease).