When starting a development project, one crucial factor to consider is the size of the building. Depending on your location, new houses or flat conversions might need to comply with the nationally described space standards, which outlines the required internal areas for new homes.
This standard goes beyond just the gross internal area (GIA); it sets minimum sizes for bedrooms, storage, and floor-to-ceiling heights, all of which are linked to occupancy levels. Therefore, understanding how these standards apply to different household sizes is essential for any property developer.
Gross Internal Floor Area (GIA) represents the total floor space within a unit's external walls. It includes spaces occupied by internal walls, service areas like WCs, columns, chimney breasts, and even lift and plant rooms. However, it excludes eaves storage in the roof, open balconies, fire escapes, vehicle parking areas, and any area with a ceiling height under 1.5m (except under stairs). The GIA also varies depending on the property's intended capacity, which includes the number of bedrooms, bed spaces, and number of storeys.
Studio flats are classified as one-bedroom flats or one-person units and must be on a single storey. The minimum gross internal area required is 39 square meters if it includes a bathroom or 37 square meters with a shower room. This area must also accommodate at least 1 square meter of built-in storage. New build homes should also be minimum 37m2.
For one-bedroom, two-person flats (1B2P), the minimum gross internal area is 50 square meters for a single-storey unit and 58 square meters for a two-storey unit. These flats must include at least 1.5 square meters of built-in storage space.
For two-bedroom flats which are single-storey, the minimum gross internal area is 61 square meters for up to three people or 70 square meters for four people / bed spaces.
These standards represent the minimum acceptable sizes that will be considered by council's for new residential dwellings or house to flat conversions. While some developments with smaller floor areas may still gain approval if justified, meeting or exceeding these standards generally increases the likelihood of success in the planning process.
If you are unsure how many flats you can achieve with your proposed development or if you would like some professional advice on how to comply with the minimum size standards, 4D Planning are happy to offer a consultation as well as a site visit to work out the GIA and provide guidance on how best to achieve a layout that will be acceptable to the council.
In 2017, the government set out further internal area requirements for bedrooms in houses of multiple occupation (HMOs). These include the following:
A room to be used by 1 person can’t be smaller than 6.51 square metres
A double room to be used by max. 2 persons can’t be smaller than 10.22 square metres
A room used by children 10 years old and younger can’t be smaller than 4.64 square metres
These standards are rock bottom. The council always expect developers and landlords to provide spacious accommodation to enhance the habitable space for the occupants. However these are the minimum size standards which will be used when assessing the planning application.
When planning a flat conversion from a single dwelling house, your property's existing Gross Internal Area (GIA) can greatly impact the project's feasibility. Council requirements differ; for example, Barnet, Bromley, Havering, Hackney and RBKC have no minimum size for the original structure, while Ealing, Haringey, Lambeth, Merton and Hammersmith & Fulham require at least 120 square meters. This 120 sqm must reflect the building’s original footprint as it stood in 1948 or when first constructed if post-1948. Extensions added after 1948 don’t count toward this requirement. It's crucial to review your council's specific guidelines before proceeding.
Wandsworth are the strictest council in London with regards to conversion standards to flats. They require 150m2 of floor space as the house stood in 1948 in order to justify the conversion.
The loss of single family dwellings to flats will result in the net loss of residential units in London. This outcome is contrary to many local council's policies and the London Plan. There are solutions to overcome these concerns. 4D Planning can advise on this and other matters to maximise your chances of approval with your conversion of dwellings to flats application. Get in touch today for a initial consultation!
In June 2023, the Mayor of London released the Housing Design Standards as part of the London Plan Guidance (LPG). This document, along with other guidelines, aims to significantly enhance housing quality in the city. While these best practice space standards don't replace national standards, they set higher goals for developers in London. The focus is on increasing storage space and improving areas suited for working from home, aligning with the London government's push for better living conditions.
Best practice home sizes in London are typically 10-14% larger than the national minimums. For instance, a 1-bedroom, 1-person flat with a shower should be 41 sqm instead of 37 sqm, while a 2-bedroom, 4-person flat should be 77 sqm instead of 70 sqm. For a 2-storey, 3-bedroom, 6-person house, the size should be 114 sqm rather than 102 sqm. Additionally, ground-floor flats are recommended to have a 3.5m floor-to-ceiling height, compared to the 2.5m standard in the London Plan. The impact of these standards on planning application rejections remains to be seen, and updates will follow. Watch this space...
We hope the above information was useful. If you wish to discuss your project with us, we look forward to guiding you and supporting your project to maximise the chances of success with the local council.
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