The Amalgamation of Residential Units in London

Decoration Decoration

Depending on the local authority, planning permission may not be required for the amalgamation of properties in London

Planner Insight
Policy & Legislation
Author Alex Yearsley
Principal Planner
Decoration Decoration

The prospect of creating a larger dwelling without the need for planning permission is an attractive proposition where it can add space and value to the property. As defined under Section 55 of the Town and Country Planning Act 1990, the amalgamation of two or more dwellings into one is not normally considered ‘development’.  This means that planning permission may not be required, including internal works on non-Listed Buildings. However, some authorities take a different approach, which you may need to consider. A few key examples are considered in this article.

Kensington and Chelsea

The Council’s long-standing view is that the amalgamation of units is a material change of use and therefore does require planning permission. The Council has defined this in their Local Plan which was adopted in September 2019 and sets out their approach to amalgamating units. The policy was written to protect the Borough’s existing housing stock, prevent a reduction in the overall number of homes and to ensure the loss of units didn’t hinder their ability to meet future housing need. The Council identify a strong market demand in the borough for very large homes, which is resulting in the substantial loss of units and does not make efficient use of the land.

RBKC Policy CH1 states that the Council would only allow for amalgamation of units if the net loss of units is one and that the new dwelling would be less than 170 sq.m. Planning permission is still needed on any such application to determine its compliance with the policy.


The London Borough of Camden take a slightly different view and have a higher threshold for what is considered to be a material change of use. The Local Plan was adopted in 2017 and Policy H3 seeks to protect existing housing by resisting development that would involve the net loss of two or more homes, meaning that there is no material change of use where there would be the net loss of one unit. The policy provides exceptions, so planning permission would still be required where there would be a net loss of two or more units. Applications could be supported where the proposal would provide ‘large homes’ where there is a low concentration of such housing and where the existing units provide sub-standard accommodation.

There are many examples in Camden where two units have been amalgamated to create one home without planning permission, often where a previously large single dwelling was subdivided in the past, and the original use is now being restored through ‘de-conversion’. It is recommended that a certificate of lawfulness is obtained before undertaking the physical work to amalgamate units in these circumstances.


Westminster, whose City Plan was adopted in April 2021, take a different approach again in Policy 8. The policy drivers are to encourage the provision of affordable housing, as well as protecting existing housing stock and restricting the development of ‘super-sized’ homes (defined as more than 200 sq.m). Westminster also recognises that the net loss of one smaller unit to provide for a family-sized unit, particularly in de-conversion situations, can be supported, or where existing units are of sub-standard accommodation. A certificate of lawfulness could be given where any proposals fall strictly within those parameters, and planning permission is needed otherwise. This policy wording is being strictly applied and applications are often refused even in de-conversion situations where the new unit would be more than 200 sq.m.


Perhaps London’s most stringent approach to amalgamation; Lambeth adopted their Local Plan in November 2021.  Local Plan Policy H3 seeks to safeguard existing residential units and is driven by the corresponding London Plan Policy H8 part (a) which states that the loss of existing housing should be replaced by new housing at existing or higher densities with at least the equivalent level of overall floorspace.

The policy does facilitate amalgamations but only in exceptional circumstances where the proposal is for specialist non-self-contained accommodation (Use Class C2) to meet an identified local need.  There is no floor area stipulated in the policy, which indicates that all amalgamation proposals resulting in the loss of units would be unacceptable in principle (unless meeting the above exception) with recent decisions providing corroboration for this. We recommend this policy is carefully considered prior to making any investment decisions in residential property where the ultimate intention is to amalgamate dwellings.


At the other end of the spectrum, Islington are generally open to the amalgamation of residential properties.  Islington’s Development Management Plan was adopted some time ago in 2013 and we will closely monitor the ongoing Local Plan review to see whether their approach changes to align more closely with Policy H8 of the London Plan.

At present, Policy DM3.2 of the Development Management Policies 2013 (DMP) stipulates that the loss of existing self-contained housing will be resisted unless the housing is replaced with at least the equivalent floorspace.  However, calculations of whether there is a loss of overall housing provision can be made based on floorspace rather than dwelling numbers where the redevelopment will provide a more appropriate housing mix. Therefore, proposals involving the loss of units would generally not be resisted.

The Council seek to maximise the proportion of family accommodation in both affordable and market housing. Recent approvals indicate that proposals resulting in the loss of self-contained units but without the net loss of any existing residential floorspace are considered acceptable.

Islington’s policy is perhaps the most holistic approach whereby proposals to amalgamate properties are decided on the basis of local character insofar as family sized dwellings are a common feature.  We recommend being mindful of the location of your property and making an early assessment of the nature of dwellings present in the locality.

Generally speaking, planning policy across London Boroughs is focused on protecting existing housing stock, maximising affordable housing and restricting ‘super-sized’ homes. This is achieved by individual Boroughs defining what is important to their strategy and making clear what they consider to be material. The nuance of each policy needs to be taken into account at an early stage which can have implications for the planning strategy for the proposals.

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