Party wall rules for flats and leaseholds

Last updated: 30 July 2026

Flats are where party wall notices go wrong most often, for one simple reason: one property next door can have two owners — the leaseholder and the freeholder — and the Act says serve them all. Here's how ownership works, what counts as a party structure in a flat, and the mistakes that make flat notices void.

Walls, floors and ceilings — what's shared in a flat

In a house, the party structure is the wall between you and next door. In a flat it's that and the floor: the structure separating you from the flat above or below is a party structure too, so the notice rules run vertically as well as horizontally. Cutting into the separating wall, removing a chimney breast, opening up the floor structure — all of it is section 2 territory, with the full two-month notice.

The everyday jobs stay exempt, same as houses: plastering, rewiring, new sockets, shelving. The test is whether the work could affect the structure's strength or support, or cause damage on the neighbour's side. No → not notifiable.

Who counts as an "owner" (this is the part people miss)

Under the Act, an owner is anyone who is:

• the freeholder,
• a leaseholder with more than a year left on the lease,
• someone under contract to purchase one of those interests, or
• someone entitled to receive rents from the property.

So the flat next door is typically owned by its leaseholder and the building's freeholder — and both must be served. A couple who own jointly must both be named. And a short-term tenant (a year or less) is not an owner: serving only the person renting the flat is a defect that can void the notice.

Share of freehold, and management companies

Two very common London arrangements where the honest answer is "check, don't assume".

If the flats in a building jointly own the freehold — often through a company the leaseholders are shareholders in — the freehold interest and the leasehold interests are still separate things, held by different legal persons even where the same people stand behind both. Whether that collapses into one notice or still requires two depends on who actually holds which interest, and the Act doesn't spell it out. The same goes for a management company or Right to Manage company: managing a building isn't the same as owning an interest in it, and the Act doesn't address these arrangements at all.

This is the one place on this page where we'd genuinely rather you asked someone. Get a surveyor to confirm the list of owners before serving — it costs a phone call, and it's the alternative to discovering the notice was defective after the surveyors are already billing.

Serving it right in a block

The freeholder may be a company — the notice goes to them just the same, with every owner named. If you genuinely can't identify an owner, the Act allows addressing the notice to "The Owner" and delivering it to a person on the premises or fixing it conspicuously to the building. The full drafting checklist, including the six defects that void notices, is in how to write your own party wall notice.

How to find out who the freeholder actually is

"Address it to The Owner" is the Act's fallback, not the first move — and it's a weak position to be in if the notice is later challenged. The ordinary route is a Land Registry title search on the neighbouring property, which costs a few pounds per title and names the registered proprietor of the freehold and any registered leases.

Worth doing even when you think you know: converted houses change hands, freeholds get sold to investment companies, and the person collecting the ground rent isn't always the registered owner. If the search turns up a company, serve the company. If it turns up somebody unresponsive, you've at least got a documented, correctly-addressed notice — which is a much better place to be than a guess.

Purpose-built block or converted house?

Practically quite different, even though the law is identical. A purpose-built block usually has one freeholder and a managing agent, so the list of owners is short and findable. A converted period house split into flats is the harder case: several leaseholders, a freeholder who may be one of them, and separating walls and floors that were never designed as party structures at all.

The conversion is also where the cost multiplies. Fees are per neighbour, so a three-flat conversion next door can mean three sets of owners to serve and, if they dissent, several surveyors — see what that does to a London bill and who pays for them.

Your lease is a separate hurdle

The point that catches leaseholders hardest, and it isn't in the Act at all — which is exactly why it's easy to miss.

If you're a leaseholder doing the work, you'll typically need two different permissions: the party wall process with your neighbours, and your freeholder's consent to alter under the terms of your lease — often a formal licence to alter. They're independent. Serving a party wall notice grants you nothing under your lease, and your freeholder's licence grants you nothing under the Act.

The Act is silent about leases, so what your lease requires, and whether your alterations need consent at all, is a question about your lease rather than about party walls. Read it, or have someone read it, before work starts — the same way planning permission and Building Regulations are separate systems that each have to be satisfied on their own terms.

Received a notice about the flat next door?

Everything on what your notice means applies — the three options, the 14-day clock, the building owner paying reasonable surveyor fees. One flat-specific check worth making: does the notice name every owner of your property? If you're a leaseholder and your freeholder was never served, the notice may be defective — worth raising before you respond.

Selling a leasehold flat with party wall history

It surfaces at sale, so it's worth keeping the paperwork. The standard conveyancing form asks sellers directly whether they're aware of any notice served or received under the Act, and for details of works carried out — and in a flat, a buyer's solicitor may also ask about the freeholder's consent, since the two are separate.

Keep the notice, any written consents, the award if there was one, and the schedule of condition together. Selling with no party wall agreement covers what gets disclosed, what indemnity insurance does and doesn't fix, and why the Act itself says nothing about selling.

Not sure whether your project — or your neighbour's — crosses the line? The free checker handles flat scenarios and will flag the serve-the-freeholder rule automatically. Six questions, about 90 seconds, no signup.