Usually yes — but not for the reason most people assume, and the duty is nothing to do with planning permission.
Two different things get muddled together here. Keeping them apart makes the whole subject straightforward.
The two separate things
Planning permission. If your conversion needs it, the council writes to the neighbours itself and gives them twenty-one days to comment. You do not have to do anything. And most loft conversions do not need planning permission at all — they go through as permitted development.
The Party Wall etc. Act 1996. This is a legal duty that sits on you, the owner. It applies whether or not you need planning permission, and it catches most loft conversions in a terrace or a semi. This is the one people miss.
So the common situation is a conversion that needs no planning permission at all, where the neighbours get no letter from the council, and where you still have a legal obligation to serve notice on them yourself.
What triggers a party wall notice
In a loft conversion it is nearly always the steels.
New beams need bearing, and in a terrace or semi they bear into the party wall — the wall you share. Cutting a pocket into that wall is work on a party structure, and it needs notice. So does raising the party wall where a dormer meets it, and so does inserting flashing or weathering into it.
The usual triggers, in plain terms:
- Cutting into the shared wall to seat a steel beam or a joist
- Raising or extending the shared wall upwards
- Removing a chimney breast that sits on or in the shared wall
- Underpinning or cutting away parts of it
What does not trigger it: a rooflight conversion in a detached house, or work that stays entirely within your own structure and never touches the shared wall. A rear dormer on a semi that lands its steels on internal walls and the external gable may well avoid it too. It depends on where the load goes, which is why the structural engineer's drawings come before the notices.
How much notice, and what it has to say
For work on a party structure — the steels, the chimney breast, raising the wall — the notice period is two months before work starts.
For building up to the boundary line it is one month, and for excavating near a neighbour's foundations it is also one month. A loft conversion rarely involves either, but a loft-and-extension job often involves all three.
The notice has to be in writing and it has to name you as the owner, describe the work, say when it will start, and be dated. Two months is a long time if you have already booked a start date, which is why we raise this at the quotation stage rather than three weeks before the scaffold arrives.
What happens when the neighbour replies
Three possible outcomes. Within fourteen days they can:
- Consent in writing. Done. No surveyor, no fee, no delay. This is what happens most of the time when people have been spoken to properly beforehand.
- Dissent and appoint a surveyor. Not hostility — it is the formal route. A surveyor (or one each) produces a party wall award setting out what may be done and recording the condition of their property first.
- Say nothing. Silence counts as dissent. After fourteen days it goes down the surveyor route whether anybody wanted it to or not.
That third one is the trap. A neighbour who throws the letter in a drawer because they do not mind has just cost you a surveyor's fee. It is worth knocking on the door and explaining what the letter is before it lands.
Who pays
You do. The building owner pays for the notices, and normally for the surveyor's fees as well — usually both surveyors if two are appointed, since the work is for your benefit.
A straightforward loft conversion award on a semi is typically several hundred pounds. It is not nothing, and it belongs in the budget from the start rather than appearing as a surprise. We say so in the quotation.
What happens if you skip it
The Act has no criminal penalty, which is why some builders shrug at it. The risk is civil and it is worse.
Without an award there is no agreed record of the neighbour's property before you started. If a crack appears in their plaster six weeks later — one that was there in 2019 — you have no way to show it. They can seek an injunction to stop the work, which stops it with your scaffold up and your trades booked.
And it surfaces again at sale. A buyer's solicitor asks whether party wall procedure was followed. The honest answer being no is a problem at exactly the moment you want one less problem.
The part that is not law
Everything above is the legal minimum. The thing that actually keeps a street pleasant is a conversation.
Tell them when the scaffold is going up and roughly how long it stays. Tell them which days are noisy — the steels going in, and the day the roof opens. Give them a mobile number, and make it a real one that gets answered. Say where the skip is going and when it leaves.
We do that on every job, and we would rather James takes the complaint than you do. It costs nothing and it is the difference between a neighbour who puts up with eight weeks of mess and a neighbour who rings the council about the hours.
Worth reading next: which lofts cannot be converted, and how we run a job, which sets out when the notices go out relative to everything else.