Party Wall Act: What Builders Actually Need to Know

‍‌​‌‌​‌​​​‌‌​‌​​​‌‌​​​​‌​‌‌‌‌​‌​‍For small builders and main contractors (England & Wales)

Last reviewed: March 2026

This isn't building regs and it isn't planning. It's its own law that kicks in on a lot of lofts, extensions and boundary work, and it lives between your client and their neighbour.

1. What the Party Wall Act actually does

Applies in England and Wales to works that affect:

• Existing party walls/party structures (shared walls/floors).
• New walls on or right next to the boundary.
• Excavations near neighbour's foundations (within 3 m or 6 m to below their footing level).

It doesn't stop the works; it sets a process so neighbours can't be bulldozed, and disputes go through surveyors instead of turning into a street war.

It's civil law. Building Control do not enforce it. But if your client ignores it and you build anyway, you can end up with injunctions, delays and expensive remedial work.

2. When it applies on your jobs

Common triggers you'll see all the time:

Loft conversions

• Inserting steels into the party wall.
• Cutting into the party wall for new joists.
• Raising/rebuilding party walls for dormers or gables.
• Altering shared chimney breasts.

Extensions and basements

• Excavating for foundations within 3 m (sometimes 6 m) of a neighbour's structure and going deeper than their foundations.
• Building a wall on or astride the boundary line.
• Underpinning or cutting into the party wall to support new beams/floors.

Boundary walls and garden walls

• Building a new wall astride the boundary ("party fence wall").
• Rebuilding or significantly altering an existing shared wall.

Chimney breast works on a shared wall

• Removing or altering chimney breasts on a party wall is squarely under the Act.

If any of that is on the drawings, assume there's a Party Wall Act question, even if the client hasn't mentioned it.

3. The three main types of notice (builder's version)

Your client is the "Building Owner"; the neighbour is the "Adjoining Owner". Notices come in three flavours:

Section 1 - New wall at or astride the boundary

• New wall on the line of junction or astride it (shared).
• Typical: new side wall for an extension right on the boundary.
• One month's notice minimum before you start.

Section 2 - Works to an existing party wall/structure

• Cutting into, raising, thickening, demolishing and rebuilding, or chasing into a party wall; also floors between flats.
• Typical: loft steels into party wall, raising gable up, cutting pockets, chimney breast changes.
• Two months' notice minimum.

Section 6 - Adjacent excavation

• Excavating within 3 m (or 6 m in some cases) of neighbour's building/structure and deeper than their foundations.
• Typical: new deep trench for an extension close to the boundary, basements.
• One month's notice minimum.

Work can hit more than one Section at once (e.g. side extension foundations + steel into party wall).

4. What happens once a notice goes in

Basic flow (ignoring the legal poetry):

1. Client serves notice(s) on the Adjoining Owner(s). You should be telling them they need to do this; you don't normally serve it yourself.

2. Neighbour can:

   • Consent - usually in writing, maybe with some agreed conditions.
   • Dissent and agree one surveyor - one surveyor acts for both.
   • Dissent and appoint their own surveyor - two surveyors then pick a third if needed.

3. If they ignore the notice, that is treated as dissent after the relevant period, so you go down the surveyor/Award route anyway.

4. The surveyor(s) prepare a Party Wall Award that sets:

   • Exactly what work is allowed and how.
   • Access rights (scaffolding, hoarding etc.).
   • Protection measures and working hours.
   • Who pays for what (normally the Building Owner).
   • How to deal with damage and making good.

5. You then build in line with the Award.

5. What this means for you on site

From a builder's point of view, the key rules are:

Don't start notifiable work until notices have been served and either:

• The neighbour(s) have consented in writing, or
• A Party Wall Award is in place.

Work to the Award

• Follow any sequencing, method and access conditions in the Award.
• Stick to any specified temporary works/monitoring.
• If you need to change something that affects the party wall or excavation, the Award may need updating - tell the surveyor.

Record everything

• Pre-start condition photos of adjoining property (especially where you're excavating or touching the wall).
• Site diary notes if you see pre-existing cracks or movement.
• This stuff is gold if damage is blamed on you later.

Important: Party Wall is between owners, but your behaviour and paperwork on site is what decides whether it stays calm or blows up.

6. Who pays for what

In most standard cases:

The Building Owner (your client) pays for:

• Their own surveyor.
• The Adjoining Owner's surveyor (if they appoint one).
• Reasonable making good to neighbour's property if you cause damage.

If the neighbour requests extra work that mainly benefits them, they may pay or share the cost - the Award will spell this out.

You're not personally on the hook for surveyor fees unless your contract or behaviour causes extra cost (e.g. ignoring the Award and causing damage/variation).

7. Typical scenarios you'll see

Loft conversion in a terrace/semi

• Steels into party wall + maybe raising gable/party parapet.
• Expect Section 2 notice, maybe more.
• You should be asking: "Have you sorted Party Wall?" as soon as loft steels appear on the drawings.

Side or rear extension near the boundary

• New wall close to or on boundary + trench deeper than neighbour's footing.
• Likely Section 1 and Section 6 notices.

Basement or major underpinning

• Heavy Section 6 involvement; surveyors will likely be hands-on.
• Expect more conditions in the Award on monitoring and temporary works.

Chimney breast removal on a party wall

• Section 2 notice needed.
• Award may require specific support details (gallows, steels etc.).

8. Classic mistakes to avoid

Assuming it's "a planning thing" or "BC will tell us"

It's neither. Party Wall is separate. BC don't enforce it.

Starting notifiable work with no notice/Award

Neighbour can get an injunction; you could be ordered to stop mid-job and maybe undo things.

Letting the client "sort it later"

Once you've cut into the wall or dug the foundation, they've lost their negotiating position.

Ignoring the Award

If you build outside what's allowed, you're exposing your client (and yourself) to claims and more surveyor time.

No evidence of condition

If you don't have pre-work photos, every crack is "your fault" by default.

9. Where you fit in as the builder

Legally, the duties under the Act sit with the owners. But in real life:

• You're the one who spots that a job hits the Act.
• You're the one who gets blamed when a neighbour kicks off mid-build.

So your basic stance should be:

• Flag Party Wall issues at quote/early design stage: "This job looks like it needs Party Wall notices and probably surveyors - you'll need to allow for that."
• Don't let the client push you to start notifiable work without at least seeing either:
  • Written neighbour consent, or
  • A signed Award.
• If in doubt, tell them to speak to a party wall surveyor and get something in writing.

This page is a general guide for small builders and main contractors. It doesn't replace the Party Wall etc. Act 1996, the official explanatory booklet, or legal/surveyor advice. Always check the latest government guidance and, where necessary, get a specialist party wall surveyor involved before you start cutting or digging near a boundary. SiteKiln does not provide legal, financial or tax advice. All content is for general information purposes only. Always seek professional advice for your specific situation.

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