Considerations at the Start of a Build

Below I have listed some key considerations the builder will need to factor in at the beginning of a build or extension.


Is there side access to bring machinery on to site to dig the footings? If there is no access for machinery, footings will require hand dig. I for one have taken the executive decision not to take on terrace house developments where there is no access as we prefer to machine dig all footings. Of course, there are plenty of builders that will happily take on hand digs, it just requires a labour intensive crew at the beginning.

Party Wall Agreement

If your extension is within 3m of a neighbour it is recommended you get a party wall agreement.

The depth required for the footings. Factors that affect the depth requirements:

  • Surrounding trees
  • Any man-made ground (e.g. ground that has been back-filled)
  • Drains
  • The depth of the existing house footings – with an extension you will always need to dig down below the existing house footings. Existing footing depth is unknown until tested. A builder will ordinarily allow for and quote based on footings 1m deep, with the caveat that if you need to go deeper this will incur additional cost.

Location and depth of drains

Drains may need to be moved. Footings need to go below any drains remaining within the build – when building over a drain the builder will need an agreement from the local water board (e.g. Thames Valley Water in the case of builds in my locality)

Gas, water and electricity mains

Consideration needs to be given as to where gas, water and electricity mains enter the property. This impacts where the manifold will go, the boiler, the fuse box, direction of piping etc…