London's design-led approach links capacity to the quality of the proposed homes and their setting. [1]
Establish the buildable envelope first
Start with the site's boundaries, levels, neighbouring buildings and relevant constraints. Then test an envelope showing the proposed footprint, height and relationship to the street. National policy L2 supports making better use of land, while retaining safeguards for access, character, daylight, sunlight, privacy and external amenity. [2]
The envelope is not simply the largest volume that can be drawn. Check where windows can provide useful light without unacceptable overlooking, and where the layout must leave room for outdoor space and practical access. Sections are particularly useful where ground levels differ. [1]
Distinguish building area from accommodation area
A building's overall footprint is not the usable floor area available to divide between homes. Shared entrances, stairs and other common spaces have to be designed as part of the building. Within each dwelling, the Nationally Described Space Standard measures gross internal area and separately controls bedroom areas, widths and built-in storage. [3] [1]
State the intended occupancy of every home. A two-bedroom, three-person flat and a two-bedroom, four-person flat have different minimum areas. Calling a room a double bedroom on a sales plan does not establish that it meets the relevant dimensions. [3]
Prepare an accommodation schedule recording the proposed occupancy, floor area, bedroom dimensions, storage and outdoor space. This exposes conflicts before the design is treated as settled. The schedule should match the actual floor plans rather than assume that every unit of the same type is identical. [3] [4]
Add the requirements that affect the whole scheme
Test accessibility alongside circulation, not after the unit layout has been maximised. London Plan D7 establishes requirements for accessible and wheelchair-user dwellings, with qualifications that must be considered for the specific development. [1]
For blocks of flats with a top storey 18 metres or more above ground, the Approved Document B guidance effective from 30 September 2026 calls for more than one common stair, subject to the published transition. That can change the core and the accommodation layout materially. It is not a reason to assume that every lower block can use one stair. [5] [6]
Cycle and refuse storage also need actual locations and routes. London's March 2026 temporary cycle standards should be used where applicable, rather than the older residential figures copied from an unamended checklist. [7] [8]
Compare options before choosing a number
A useful feasibility report can compare different housing mixes and building arrangements against the same constraints. Record why an option succeeds or fails: for example, an inadequate bedroom, compromised shared access or unacceptable effect on a neighbour. The aim is a defensible capacity, not an unsupported maximum. [1]
Keep a separate record of assumptions dependent on the draft London Plan or draft Small Site Design Code. Neither was adopted when checked on 2 October 2026, so future flexibility should not be counted as an existing entitlement. [9] [10]