The proposed arrangement is straightforward in principle. A large one bedroom flat would occupy the ground floor and retain access to the garden, while a three bedroom maisonette would sit above, without private outdoor space. However, an architect has warned that planning rules may prevent the creation of a three bedroom flat without a garden.
So is that advice correct?
The short answer is that converting a single house into two separate flats counts as development under the Town and Country Planning Act 1990. That means planning permission is required, and the outcome will depend heavily on local planning policy.
Across London, most planning authorities impose minimum requirements for amenity space in new residential development, including conversions. Amenity space refers to private outdoor space and does not have to mean a traditional garden. In the case of flats, it can include a balcony, terrace or, in some circumstances, roof space.
The precise standard varies by borough, but the London Plan sets a baseline. Under the London Plan 2021, new homes designed for one or two people are expected to have at least five square metres of private outdoor space, unless a local authority requires more. Importantly, these standards generally apply equally to conversions and new builds.
This means there is no automatic rule that a three bedroom flat must have a garden. However, there is usually an expectation that it will have some form of private outdoor amenity. A complete absence of such space is often a reason for refusal.
Where physical constraints make compliance difficult, planning authorities may consider alternatives. These can include roof terraces, shared amenity areas or, in some cases, a financial contribution secured through a planning agreement. Each option requires clear justification and is assessed on a case by case basis.
Recent decisions suggest that councils are reluctant to relax these standards. In one appeal involving Brent Council, permission was refused for the conversion of a first floor flat into two studio units because no private external amenity space was provided. The inspector ruled that nearby public green space was not an adequate substitute for private outdoor provision.
The lesson for homeowners is that while your architect is right to flag the issue, the position is not absolute. A three bedroom flat does not legally require a garden, but it is very likely to require some form of private outdoor space to satisfy planning policy.
Before proceeding, it is essential to review the specific policies of your local planning authority and to explore creative design solutions that can meet amenity standards without compromising the overall scheme. Early advice from a planning consultant, alongside architectural input, can make the difference between approval and refusal.
