The council's planning decision and the freeholder's permission are separate: neither allows you to ignore the other. [1] [2]
Establish what you are entitled to alter
Check the lease and its plan before developing a detailed design. A garden may be included in the flat's demise, shared with others or subject to rights of access. The external wall and structure may belong to the freeholder even where the garden is yours. Ask a solicitor to identify the rights needed for the specific footprint and building work. [2] [3]
The consent package should describe the actual work, not simply request permission for “an extension”. Include drawings, structural information where relevant and details of how the building and other occupiers will be protected. [2]
Design for the whole building
The planning proposal should explain how the addition relates to the host building, neighbouring windows and the remaining external space. London's housing quality policy addresses daylight, privacy, ventilation and the quality of accommodation, not just the number of square metres gained. [4]
As a design exercise, draw the upstairs windows and the whole garden alongside the proposed extension. Test whether the new roof, rooflights, doors and outdoor arrangements work for everyone affected. This is more useful than copying a house extension that happens to have been approved nearby. [4] [1]
A listed building needs a separate check for listed building consent. Planning Portal specifically identifies this additional consent where a flat extension affects the building's special character. [1]
Coordinate the technical design
Building regulations deal with the construction rather than the planning merits. Resolve the structure, fire precautions, insulation, ventilation and drainage as part of that process. Check the building-control route before work begins; higher-risk buildings fall under the Building Safety Regulator except for specified categories of work. [5] [6]
For the design brief, identify any shared services or retained building elements within the work area. A connection design should account for the new demand rather than assume the old water or electricity arrangement is adequate. Utility providers distinguish supply upgrades from simply adding meters. [7] [8]
Agree the order of decisions
- Confirm the lease, title boundaries and any landlord approval process.
- Prepare a scheme showing the extension in the context of the whole building.
- Obtain the necessary planning and heritage decisions.
- Finalise the technical approvals and satisfy the landlord's conditions before construction. [2] [1] [5]
Ask the project team to identify separately whether party-wall procedures or sewer consents are relevant; the planning decision is not a substitute for investigating those interfaces.
At handover, retain the approved drawings, written landlord consent and building-control evidence together. They answer different questions when the flat is later sold or the work is checked. [2] [5]