Is planning permission required to amalgamate two flats into a single dwellinghouse?
Planning law is not clear on whether you need permission to amalgamate two or more separate residential units (i.e. flats) into a single dwellinghouse. This is unlike the position for subdividing a single dwellinghouse into smaller, separate residential units for which it is clear that planning permission is required. This issue was highlighted recently in an unsuccessful appeal against the refusal of the Royal Borough of Kensington & Chelsea to grant a lawful development certificate ("LDC"). In his decision letter, the planning inspector concluded in this particular case that the amalgamation of two flats in Cheyne Gardens into one larger flat was development constituting a material change of use for which planning permission was required.
Planning legislation states that where development does not result in a change in the use class of the property, planning permission is not required. This would appear to cover the position where two flats are amalgamated into a single dwellinghouse: the use class was and remains C3 (dwellinghouses) and internal works do not require planning permission. However, the case of The London Borough of Richmond-upon-Thames v SSETR and Richmond-upon-Thames Churches Housing Trust  2 PLR 115 and the recent Royal Borough of Kensington & Chelsea appeal decision have ruled that the "same use class" exception cannot be relied upon in residential amalgamation cases. This is because the wording of the Use Classes Order refers to "a dwellinghouse" i.e. a single dwellinghouse. When two separate dwellinghouses are amalgamated, the "same use class" exception does not apply because the original use of the two units to be amalgamated was not "use as a dwellinghouse".
Without the benefit of the "same use class" exception, the question then becomes: is the amalgamation of two dwellinghouses capable of being a material change of use for which planning permission is required? The Richmond case and the recent Royal Borough of Kensington & Chelsea appeal decision have both held that amalgamation is capable of being a material change of use in planning terms. However, this is not a blanket rule and each case requires assessment on a fact and degree basis against the background of the applicable development plan policy and any other material considerations.
This leaves property owners and developers without a clear answer on whether planning permission will be required for amalgamation. In some instances, the local planning authority's position on amalgamation may be relatively easy to establish. However, where the position is less clear, those wishing to amalgamate units will need to examine local planning policy and considerations such as the current housing situation in the local planning authority's area. Given that local planning policy and housing figures in particular can fast become out-of-date, developers may not be able to draw any comfort from historic decisions in amalgamation cases.
To obtain a definite answer in unclear cases, developers may wish to consider applying for a LDC in order to establish whether a proposed amalgamation is a material change of use. This may avoid the unnecessary expense of a full planning application if a LDC is issued confirming planning permission is not required.