At this stage the final design from the feasibility stage is worked up in order to both finalise the design and apply for the necessary permissions.

A dimensional survey will need to be done at this stage if one does not already exist.

The other consultants such as a structural engineer, an energy consultant and a geologist will need to be employed at this stage in order that they prepare their reports which will form part of the planning permission.

At the end of this stage application is made to the council for permission to build the new design. (In the UK, planning permission.)