Up until 2000, it was generally considered that the amalgamation of dwellings was not a material change of use and therefore did not require planning permission. However the Richmond case (Richmond Upon Thames London Borough Council v Secretary of State for the Environment ) turned the matter on its head slightly. The case concerned the refusal by the local planning authority (LPA) (and then later grant on appeal) of a Lawful Development Certificate (LDC) confirming that the change of use of seven self-contained flats into a single dwelling house would be lawful. The LPA successfully challenged the appeal inspector's decision at the High Court which held that the change gave rise to planning considerations including the loss of a particular type of accommodation which was a material consideration and should have been taken into account in determining whether a material change of use had arisen. The judge concluded that if the loss of units due to amalgamation had important planning considerations and effects it should normally be considered to involve a material change of use. The position shifted from previously no material change of use (and no planning permission being needed) to the courts now stating that whether there was a material change of use depended on whether the change gave rise to planning considerations, e.g. the loss of a particular type of housing.
Application of the Richmond case
The Richmond case was applied in the recent Stanhope Gardens case (R on the application of Royal Borough of Kensington and Chelsea v Secretary of State for Communities and Local Government  EWHC 1785 (Admin)). In this case the High Court went further in deciding that the LPA is entitled to rely on its analysis of the effect of conversions upon housing supply in deciding whether the amalgamation of dwellings is a material change of use, even where a policy is silent as regards a particular planning consequence. The case concerned a proposal to amalgamate two flats. The Royal Borough of Kensington and Chelsea (RBKC) had a policy restricting the net loss of five or more residential units. In 2014, RBKC changed its position due to increasing concern about the loss of residential units and took the approach that any amalgamation resulting in the loss of even one unit would be a material change of use and require planning permission. It did not however update or change its local plan policies. The Court agreed with RBKC that it was lawful to consider the extent of amalgamations in the borough and whether that was having a material effect on reducing the number of dwellings in the housing stock which was a matter of public interest. In this case, the Court agreed with RBKC that the change was therefore material and needed planning permission which was not granted.
So where does this leave us now?
A spate of recent appeal decisions have arisen on the matter particularly in London boroughs. October 2017 saw a joint appeal against RBKC where the Inspector considered that amalgamating dwellings had a wider impact on the council's housing supply and therefore considered it to be a material change of use and the LDC was not granted. The second appeal to grant retrospective planning permission was successful but only because of the applicant's personal circumstances and thus a personal permission was granted. This year we have seen an appeal decision (also against RBKC) in which the planning inspectorate sought to take a balanced approach;
a) the inspector acknowledged that the emerging local plan and London plan policies resisting the loss of residential dwellings would be breached, however;
b) the current policy stated the council would seek to resist amalgamations that would result in a net loss of 5 or more dwellings (which the appeal scheme satisfied);
c) the council was still able to meet its 5 year housing supply target;
d) the larger property would meet a local need for larger houses; and
e) the scheme would see a building returned to a dwelling house.
On balance, in light of the above considerations, the appeal was allowed.
Ultimately, the position is going to vary between different councils however it is likely that amalgamation specific policies will be brought to the fore. RBKC is undertaking a partial review of its local plan and seeking to introduce a policy to resist amalgamations unless it would result in the loss of only one unit and the total floor space of the new dwelling created will be 170sm or less. Until such policies are adopted, LPAs are likely to continue to decide each application on its own merits and in accordance with their development plan policies, and whether or not they can meet their 5 year housing land supply.