Converting two flats back into a single house is becoming more common across London.
A Victorian or Edwardian property may have been divided into separate flats decades ago, and a new owner may now want to restore it as one family home. The work can involve removing kitchens, opening staircases, changing floor layouts, removing walls and creating new structural openings.
Because much of the work takes place inside the building, it is easy to assume there will be no Party Wall issue.
That is not always the case.
Where flats are arranged above and below one another, floors and ceilings can form what the Party Wall etc. Act 1996 describes as a party structure. Structural work to walls shared with neighbouring properties can also fall within the Act. Government guidance confirms that a party structure can include floors and other structures separating different parts of buildings approached by separate entrances or staircases.
Why Flat Reconfiguration Is Different From Ordinary Internal Renovation
If you remove a lightweight partition entirely within your own flat, Party Wall procedures may have nothing to do with it.
But converting two separate units into one often involves more than cosmetic changes.
A typical project might include:
- forming a new opening between floors
- rebuilding or extending a staircase
- removing structural walls
- installing steel beams
- cutting into external party walls
- altering floors between former flats
- changing drainage routes
- carrying out structural work around chimney breasts
- strengthening floor structures
- opening up the rear of the property
Some of these works may be entirely within one ownership. Others may affect structures shared with adjoining owners.
The key is to identify which is which before demolition begins.
Floors Between Flats Can Be Party Structures
The phrase “party wall” can be misleading because the Act does not only deal with walls.
In blocks and converted houses, the floor between two separately occupied flats can be a party structure.
This matters if, for example, a staircase opening is being formed through a floor that previously separated two independently owned units.
If both flats are now owned by the same person, the position may be simpler internally, but that does not remove Party Wall considerations involving other adjoining owners elsewhere in the building.
For example, a converted house may contain three flats. You may own the ground and first floors and want to combine them, while the top-floor flat remains separately owned.
Structural works can therefore still affect a party structure associated with another owner.
Freeholders and Leaseholders Need to Be Identified Early
This is one of the biggest practical differences between dealing with a single terraced house and a converted building.
Under the Party Wall Act, the definition of “owner” can include freeholders and certain leaseholders with an interest exceeding one year. This means there can be more than one adjoining owner for the same building.
Before notices are prepared, it is important to understand:
- who owns the freehold
- who owns each leasehold flat
- whether neighbouring flats are separately owned
- which structures are shared
- whether another building adjoins the property
Getting this right at the start can avoid having to re-serve notices later.
Removing a Wall Between Rooms
One of the most common parts of a flat-to-house conversion is opening up rooms.
For example, the owner may want to remove a wall between the rear reception room and kitchen or create a wider opening through the centre of the house.
Removing the wall itself may not be a Party Wall matter.
The issue often arises when the replacement steel beam is supported by a party wall.
Cutting a pocket into a party wall to support structural steel is one of the types of work that may require formal notice. GOV.UK guidance specifically identifies cutting into a party wall as work that can fall within the Act.
This is why structural engineer drawings are so important.
A surveyor needs to see where the beam bears, not simply know that a wall is being removed.
Creating a New Staircase
Restoring a house that was previously divided into flats often means reinstating a staircase or forming a completely new stair opening.
If the stair opening is formed entirely within your own floor structure and does not affect a party structure connected to another owner, Party Wall procedures may not be required.
However, where the works alter a structure shared with another flat or involve cutting into party walls for support, the position changes.
The project should therefore be reviewed as a whole rather than assuming that every internal alteration is exempt.
What About Chimney Breasts?
Many converted London properties have already had fireplaces altered over the years.
During a conversion back into one house, owners sometimes decide to remove remaining chimney breasts to improve room layouts.
Where a chimney breast is built against or forms part of a party wall, its removal can fall within the Act. Government guidance specifically lists removing chimney breasts from a party wall as an example of relevant work.
This can be especially important in older terraces where previous alterations may not be fully documented.
Do You Need Notice for Every Part of the Renovation?
No.
A Party Wall Notice is not a general permission slip for the whole refurbishment.
It relates to specific works covered by the Act.
Decorating, replacing kitchens, installing bathrooms, changing non-structural partitions and carrying out ordinary internal finishes usually do not require Party Wall Notices simply because they are happening in a converted building.
The structural drawings need to be separated into:
works entirely within your own property, and
works affecting shared structures, boundaries or adjoining foundations.
That distinction keeps the Party Wall process proportionate.
What If There Are Several Neighbours?
Converted flats often create multiple adjoining-owner relationships.
You may need to deal with:
- the owner of the flat above
- the owner of the flat below
- the freeholder
- neighbours on one or both sides
- commercial owners if the property is mixed-use
Not every person will necessarily need the same notice.
One adjoining owner may be affected by work to a party structure, while another is affected by excavation for a rear extension.
This is another reason generic template notices can cause problems on more complicated projects.
Combining the Conversion With an Extension
Many homeowners do not simply combine the flats. They also add a rear extension, side return or loft conversion while the property is being refurbished.
At that point, several Party Wall issues can overlap.
You might have:
- steelwork cutting into a party wall
- excavation near neighbouring foundations
- a new wall near the boundary
- work to chimney breasts
- structural alterations between former flats
The Act allows different categories of work to be dealt with, but the correct notices need to reflect what is actually proposed.
Government guidance notes that work can fall within more than one category of the Act.
Why Early Review Saves Time
A flat-conversion project usually already involves architects, structural engineers, Building Control and possibly planning or leasehold approvals.
Party Wall matters are much easier to manage when they are reviewed alongside those drawings rather than after the contractor has started.
An early review can identify:
- which owners need notice
- which structural elements are relevant
- whether more than one type of notice is required
- whether a Schedule of Condition would be sensible
- whether surveyor appointments may be needed
It also gives neighbours time to understand the project before noisy structural work begins.
Party Wall Agreements Are Separate From Freeholder Consent
This point is particularly important with flats.
Your lease may require freeholder or management-company consent before structural alterations take place.
That is separate from the Party Wall process.
Likewise, receiving planning permission or Building Regulations approval does not replace Party Wall requirements where the Act applies.
A flat conversion may therefore involve several different approvals, all dealing with different legal or technical issues.
Final Thoughts
Converting flats back into one London home can be a rewarding project, especially in period properties that were divided many years ago.
But because the work often involves structural openings, shared floors, steel beams, chimney breasts and several different owners, it deserves a proper Party Wall review before demolition starts.
Not every part of the renovation will require notice. The aim is to identify the specific works that affect party walls, party structures, boundaries or adjoining foundations and deal with those correctly.
Express Party Wall can review architectural and structural drawings for flat conversions across London, identify the adjoining owners involved and advise on the notices required before work begins.