Party Wall Act Guide for London Homeowners: What You Need to Know Before You Build

The Party Wall etc. Act 1996 is a piece of legislation that governs works to party walls, party fence walls, and excavation near neighbouring properties. It applies across England and Wales, but in London -- where terraced houses and semi-detached properties account for the majority of residential stock -- it is triggered by a very high proportion of extension and loft conversion projects.

Understanding the Act before you begin a project saves time, avoids disputes, and ensures that your programme is realistic.

A party wall is a wall shared by two separate properties. Common examples:

• The wall between two terraced or semi-detached houses
• The wall between a house and an adjoining flat
• A floor/ceiling structure between flats in a converted house

A party fence wall is a wall that sits astride the boundary between two properties but is not part of a building (a garden wall on the boundary, for example).

The Act is triggered by three categories of work:

Section 1 -- New walls on or at the boundary: Building a new wall that sits on or astride the boundary between properties (including a new party wall or party fence wall).

Section 2 -- Works to an existing party wall: This is the most commonly triggered section for London home improvements. Section 2 works include:

• Cutting into the party wall to insert a damp proof course or to insert a new beam or lintel (common in rear extensions)
• Making the wall taller or thicker
• Underpinning the party wall
• Demolishing and rebuilding the party wall
• Exposing the party wall by removing a chimney breast on the neighbouring side
• Weatherproofing after works

Section 6 -- Excavation near neighbouring buildings: Excavation within 3m of a neighbouring building and below the foundation depth of that building (or within 6m where the excavation would intersect a 45-degree line drawn from the base of the neighbour's foundations) triggers Section 6. This is particularly relevant for basement extensions and deep pile foundations.

Once you have established that the Act applies, you must serve the appropriate party wall notice on all affected adjoining owners before you begin work.

Section 1 notice: at least one month before starting work.

Section 2 notice: at least two months before starting work on the party structure. This is the notice that trips up many London homeowners -- a two-month notice period means you need to serve notice well before your planned start date.

Section 6 notice: at least one month before starting excavation.

The adjoining owner has 14 days to respond. They can:

1. Consent: they agree to the works as described. You can proceed (keep a copy of the written consent). No party wall surveyor is needed.
2. Dissent and agree to a single agreed surveyor: both parties appoint one surveyor jointly to prepare the party wall award.
3. Dissent and appoint their own surveyor: a dispute is deemed to have arisen. Each party appoints their own surveyor, and the two surveyors appoint a third surveyor as referee if needed.
4. Fail to respond within 14 days: a dispute is deemed to have arisen by default.

If a dispute arises, the surveyors prepare a Party Wall Award (also called an award) that documents:

• The works to be carried out
• Working hours
• Any special conditions
• A schedule of condition of the adjoining property (a photographic record of its condition before works begin)

Party wall surveying fees in London vary depending on complexity:

• Agreed single surveyor for a straightforward project (e.g. standard rear extension): £800--£1,800 for the award
• Building owner's surveyor where a dispute has arisen: £1,200--£3,000
• Adjoining owner's surveyor: the building owner typically pays both surveyors' reasonable fees
• Schedule of condition: £300--£600 (often included in the surveyor's fee)

For a basement project with Section 6 implications and complex structural works, total party wall costs can reach £3,000--£6,000+.

Rear extension: almost always triggers Section 2 (cutting in for the flank wall connection and the new steel beam bearing). Serve notice two months before the planned start.

Loft conversion on a terrace: usually triggers Section 2 where the roof structure or party wall is affected. Consent is often given by neighbours who have done or plan to do the same work.

Basement extension: almost always triggers both Section 2 (underpinning the party wall) and Section 6 (excavation near the neighbour's foundations). Party wall costs for basement projects are higher and the process is more complex.

Internal alteration on detached property: unlikely to trigger the Act unless there is a shared boundary wall or the works involve excavation near the boundary.

• Start the party wall process early. A two-month notice period for Section 2 works is the most commonly missed step in London extension programmes.
• Build party wall costs and time into your project budget and programme from the outset.
• Use a qualified party wall surveyor -- not a general builder -- for party wall matters.
• A schedule of condition protects both you and your neighbour by recording the pre-works state of the adjoining property.
• A neighbour who initially refuses consent often comes round to appointing a single agreed surveyor once they understand the process.

rcbGroup works with experienced party wall surveyors across London and factors party wall timescales into every project programme from the start.