Will the foundations of my extension be OK to take another storey?


Generally the design for foundations of a single storey building is the same as that for a two storey extension. The important aspects include:

  • depth to the bottom of the foundations below ground level,
  • depth of concrete in the foundations,
  • width of the foundation concrete,
  • location of the wall within the width of the foundation and
  • probably even more important, the nature of the ground under the foundation.

Unless the original foundations were laid within the last 5 years it will be necessary to expose the existing foundation in one or two locations so that the above aspects can be assessed by a structural engineer or the Building Control Surveyor before planning a first floor extension on an existing single storey part of the building.

Other important aspects to consider are:

  • suitability of existing roof structure to act as a floor
  • suitability of existing lintels over ground floor openings
  • suitability of existing walls

This advice relates solely to Building Control Opens in a new window matters and you should consult the planning pages of the website or the planning portal Opens in a new window website for advice on planning matters.