Do not assume it is simply the reverse of subdivision
Planning Portal explains that authorities can take different approaches to amalgamation, particularly because of the effect on housing supply. The loss of dwellings can be relevant even where the exterior remains unchanged. An internal doorway is therefore not the only feature to assess. [1]
Identify the lawful existing units and describe the proposed final use clearly. A return to one family home should be assessed against the current policy and planning position, not solely the building's historic appearance.
Where the proposal does not require planning permission, a certificate of lawfulness for the proposed use can provide a formal record. Where permission is needed, the application should address the loss of homes and the relevant local policy. [1]
Check the borough's actual approach
Read policies on retaining housing and creating family accommodation together. They need not point in the same direction in every case. A borough may support some deconversions while limiting how many homes can be lost. [4]
For feasibility, set out the number, sizes and lawful uses of the existing flats alongside the proposed house. That comparison allows the planning team to identify the policy issue before detailed interior design is commissioned. [1] [4]
Building regulations remain a separate question
Regulation 5 includes a change in the number of dwellings, whether the resulting number is greater or smaller. The building-control assessment should therefore address the amalgamation itself and the physical works, not only any new steel beam or doorway. [2]
Plan the structure, stairs, services and fire precautions for the completed arrangement. Removing a separating wall or changing an escape route should not be treated as an ordinary decorative alteration. The appropriate building-control body should be involved before construction. [5] [6]
If the building is higher-risk, or the work changes whether it is higher-risk, check the Building Safety Regulator's rules rather than assuming the normal small-project route applies. [7]
The 2026 energy and ventilation changes commence for relevant non-higher-risk building work on 24 March 2027, subject to transitional arrangements. Recombining dwellings must use the provisions applicable to existing buildings and material changes of use rather than the whole new-build Future Homes Standard. Higher-risk building work has separate commencement arrangements. [13]
Resolve ownership before opening between flats
Owning two flats does not necessarily mean owning every intervening structural element or having an unrestricted right to alter it. Review the leases, retained building parts and alteration clauses. Ask the solicitor how the titles, mortgage interests, rights and future ownership should be dealt with. [8] [3]
Have any revised legal plans reflect the completed intended extent. Plans suitable for land registration need to be clear and consistent with the deed; a combined marketing plan is not a substitute for that exercise. [9]
Coordinate services and records
Decide which services are being retained, altered or removed, then obtain the relevant provider's process. Meter arrangements and physical connections are not interchangeable, so removing a bill does not by itself describe the required utility work. [10] [11]
Keep the planning decision or certificate, building-control evidence and legal documentation together. Review emerging London policy separately from the adopted policies used to assess the proposal. [1] [5] [12]