Grade-II listed Georgian townhouse at Trinity Church Square, London. Photo by Inigo.
During the post-war years, many houses in urban areas were converted into flats to accommodate a growing population. Many of these buildings are Georgian and Victorian townhouses, which, at the time, were considered to have low architectural value.
Fast forward several decades, these buildings are now highly desirable, and owners are looking to restore them to their former glory.
While it might seem that converting them back into houses should be straightforward, this isn’t always the case. Many areas are again facing housing shortages, and local councils are under pressure to maintain or increase the housing supply. Losing flats, even in smaller developments, is often seen as counterproductive. Depending on where you live and how many flats you plan to combine, you may face resistance.
Read on to learn more.
Renovated Georgian townhouse interior. Photo by Inigo.
Before going into planning specifics, it’s important to check whether combining the flats makes financial sense. Compare the combined value of the flats with the estimated value of a single house. If the flats are worth more, it may be more prudent to sell the flats and buy a house elsewhere.
Consult an established local estate agent before investing too much time in your project. You may need to invest in architectural fees to create schematic designs for accurate valuations.
As a general rule, if you’re not making any external alterations and the building is entirely in residential use (with no commercial units), planning permission to combine two flats into a house is typically not required. This is because, under the Town and Country Planning Act 1990 Section 55, internal alterations within the same "use class" are not considered ‘development.’
However, some councils, particularly in London boroughs, challenge the 'two-dwelling' rule to prevent the loss of housing stock. It's essential to check your Local Plan – your council's document outlining local planning policies – to understand the situation in your area.
If there’s no specific reference to amalgamating homes in your Local Plan, then Section 55 guidance applies.
If the works aren’t classed as ‘development’, they effectively fall under permitted development rights – more on this below.
Refurbished Victorian townhouse by Lynch Architects. Photo by The Modern House.
As of the time of writing, Kensington & Chelsea and Richmond upon Thames do not classify the combination of two flats as permitted development (PD). In these areas, you'll need to apply for planning permission.
However, Camden considers amalgamating two dwellings as PD, allowing it to be done without planning permission.
Westminster permits the amalgamation of two flats, provided the enlarged property is under 200 square metres. Larger de-conversions, regardless of how many flats are combined, require full planning permission.
Outside of London, South Hams in Devon advises that planning permission is required. However, in most parts of the UK, combining two flats is generally not considered development.
For peace of mind, you can apply for a Certificate of Lawfulness for Proposed Use or Development before proceeding with detailed plans or building work. This certificate confirms whether your proposal meets PD guidelines and provides reassurance to mortgage lenders and potential future buyers.
The application fees are half the cost of full planning permission, and a decision is typically made within eight weeks. When budgeting for costs at this stage, you’ll need to factor in architect fees for preparing the application.
READ: How Much Does Planning Permission Cost in the UK?
A dilapidated stone cottage that contained two small flats was renovated and remodelled into an open plan one-bedroom house by architects Technique and Stallan-Brand. Photo by Dapple Photography.
External alterations to flats always require full planning permission. However, once your property is converted into a house, provided it’s not on designated land, it will benefit from full permitted development rights, allowing many external alterations without planning permission.
If your de-conversion requires planning permission, the council may restrict future PD rights by adding conditions to your approval to control further development. Additionally, PD rights may be restricted through legal covenants, especially in estate properties. Check your title deeds if you think this may apply.
If your building contains three or more flats, you will need planning permission to convert it back into a single house.
The number of homes being 'lost' will influence the council’s decision. A net loss of two flats may be approved, but losing more could be more difficult, especially if the council is struggling to meet its housing targets.
To gain approval, you will need to demonstrate that:
If your building is listed or locally listed, this may work in your favour, as there are heritage benefits to restoring it to its original state.
You have two options: revise your proposal to align with the council’s recommendations or appeal to the Secretary of State.
Appeals are usually challenging, and a council will only refuse an application if they feel they have strong grounds.
If you lose on appeal and believe the decision was incorrect and are willing to invest the time and money, you can escalate your application to the high court. Notable cases include:
Current legislation states that if your building was officially split into flats but has been used as a single home for more than ten continuous years, and you can provide evidence, you may apply for a Certificate of Lawfulness of Existing Use or Development to confirm its current arrangement.
Additionally, if the works were ‘substantially completed’ before 25th April 2024, the previous four-year rule may apply.
The definitions in the latest legislation are still open to interpretation, and court precedents are yet to be established. If you feel this route is appropriate, gather as much evidence as possible before applying.
If de-conversion into a single house isn’t feasible, another option is to create a larger flat.
A maisonette over the lower two floors is a popular way to create a more spacious home. Depending on the building’s layout, you may be able to add a separate entrance to create self-contained accommodation, which can be more desirable.
Alternatively, you could combine the top two floors into a duplex. Though it would have a shared stairway entrance, it would offer more privacy and avoid noisy neighbours upstairs.
READ: How to Build a Ground Floor Extension
Extended maisonette by Nimtim Architects. Photo by Jim Stephenson.
Any external alterations that fall outside of PD will require planning permission.
If your house is on designated land, such as in a conservation area, PD rights will be more limited, and you may need to apply for planning permission for exterior changes.
For listed buildings, listed building consent may be required for both internal and external alterations.
If consolidating flats into a maisonette or duplex, planning permission is necessary for external alterations. You may also need a licence to alter from the freeholder or other flat owners (if you have a share of freehold) to carry out building work.
Building regulations approval is required for de-conversion to a house or consolidating flats. If any structural work affects an adjoining wall, you will also need a Party Wall Agreement with neighbouring owners.
The information provided in this article is intended for general guidance and educational purposes only. For specific expert advice on your project, consult a skilled residential architect featured on Designs in Detail.
About the Author
Aron Coates is an architect with over two decades of experience, working on projects ranging from historic building restoration to contemporary home design.
