Mortgage repayments for a 5% deposit borrower have climbed by nearly £150 a month since November 2025, according to Moneyfacts finance expert Rachel Springall. On the same day that figure was quoted, Chancellor John Healey sat down having said nothing about Stamp Duty at all. For London households weighing up a move against a loft conversion, that silence is the headline.
The Autumn Budget on 28 October 2026 left Stamp Duty Land Tax untouched. No threshold changes, no first-time buyer relief expansion, no reform of the bands that have long frustrated London movers. With gilt yields sitting around 5.32% on Budget day and markets pricing in a Bank Rate rise in November, the cost of moving house in London has not gone down. For many homeowners, that tips the arithmetic firmly towards extending rather than relocating.
This article looks at what Stamp Duty staying unchanged in Budget 2026 means for the extend or move decision, and what it means for Party Wall notices if you are one of the many homeowners now planning a loft conversion, rear extension or basement dig this winter.
Key Takeaways
- Stamp Duty was left unchanged in Budget 2026, so moving costs in London remain high alongside expensive mortgage rates.
- Zoopla’s October 2026 data shows London prices falling and homes taking 56 days to find a buyer, weakening the case for selling up.
- Many London households are expected to extend or convert rather than move, given the stamp duty calculation now facing them.
- Extensions, loft conversions and basement works very often trigger duties under the Party Wall etc. Act 1996.
- Getting Party Wall notices right, with correct notice periods and a proper schedule of condition, avoids costly delays once building work starts.
What the Budget 2026 Actually Changed
The Negotiator reported that industry hopes for Stamp Duty relief were dashed. What did change:
| Measure | Effect |
|---|---|
| Your First Home scheme | 2.5% deposit new-build mortgages, £4.7bn funding |
| Mansion tax | Confirmed on homes above £2m, first bills March 2028 |
| Landlord income tax | Up a further 2 points from April 2027 |
| Biodiversity Net Gain exemption | Brownfield sites up to 1.5ha exempt, per HBF |
| Council and affordable housing | Additional investment announced |
| Stamp Duty Land Tax | No change |
None of these measures reduce the upfront cost of buying a home in London. That is the core of the extend or move question many households are now working through, with Stamp Duty unchanged in Budget 2026.
Why the Numbers Favour Extending
Zoopla’s October 2026 House Price Index, published 27 October 2026, painted a soft picture for London sellers:
- London prices down 1% year on year, a fall of roughly £5,400
- Prices falling in 85% of London and South East postcode areas
- Average London homes taking 56 days to find a buyer
- Sales agreed down 7% nationally
Knight Frank’s Tom Bill noted that sellers need to reflect tougher mortgage conditions in their asking prices. Combine a softer market with Stamp Duty bills that have not moved and borrowing costs still elevated, and the sums for many owner-occupiers point one way: stay put, build up, build out, or dig down.
“Sellers need to reflect tougher mortgage conditions in asking prices.” Tom Bill, Knight Frank
The Party Wall etc. Act 1996: What Changes When You Build Rather Than Buy
Extending rather than moving does not remove legal obligations. It swaps conveyancing paperwork for Party Wall paperwork.
The Party Wall etc. Act 1996 applies when certain works affect a shared wall, boundary, or nearby foundations. It exists to protect both the building owner carrying out works and the adjoining owner next door.
Loft Conversions
Steel beams bearing onto a party wall typically fall under Section 2 of the Act. This covers work directly to the party wall itself, such as cutting into it to take new loadings. Section 2 notices require at least two months’ notice before works start.
Rear Extensions
Excavation for new foundations within 3 metres of a neighbouring building (where new foundations go deeper than the neighbour’s), or within 6 metres where the excavation would cut a line drawn down at 45 degrees from the neighbour’s foundation, falls under Section 6. This is the notice type that catches many homeowners by surprise on standard London rear extensions, and it requires at least one month’s notice.
Basement Digs
Basement excavations almost always trigger the Act, often under both Section 6 (excavation near foundations) and sometimes Section 1 if a new wall is built astride or up to the boundary. These are typically the most complex Party Wall matters London surveyors deal with, given the depth of excavation and the age of neighbouring Victorian and Edwardian foundations. Where Section 2 work to the party wall is also involved, the longer two-month notice period applies to that element.
Notice Periods and the Process
| Notice type | Works covered | Minimum notice period |
|---|---|---|
| Section 1 | New wall at the boundary | One month |
| Section 2 | Work to an existing party wall or structure | Two months |
| Section 6 | Excavation near a neighbour’s foundations | One month |
Once a notice is served, the adjoining owner has three options: consent in writing, stay silent (which after 14 days is treated as dissent), or formally dissent. If there is dissent, the matter proceeds to an award, produced either by an Agreed Surveyor acting for both owners, or by two surveyors, one appointed by each side, with a third surveyor available if needed.
A schedule of condition, a detailed photographic and written record of the neighbouring property before works start, is standard practice. It protects both sides if damage is later disputed.
Typical London Timescales and Costs
These figures are typical ranges only and will vary by project and borough.
| Item | Typical range |
|---|---|
| Notice-to-award timescale (straightforward) | 6 to 10 weeks |
| Notice-to-award timescale (dissent, two surveyors) | 10 to 16 weeks |
| Surveyor fee per party (single extension) | £800 to £1,800 |
| Surveyor fee per party (basement dig) | £1,500 to £4,000+ |
| Schedule of condition cost | £300 to £900 |
Building owners usually pay all reasonable Party Wall surveyor costs, including the adjoining owner’s surveyor, under the Act.
A Winter Checklist for Homeowners Starting Works
- Confirm which sections of the Party Wall etc. Act apply to your loft, extension or basement design.
- Identify every adjoining owner, including flats above or below a shared structure.
- Serve notices in writing, with the correct notice period, before any work starts.
- Keep a record of service dates; these matter if a dispute arises later.
- Arrange a schedule of condition on neighbouring properties before excavation or structural work begins.
- Decide early whether an Agreed Surveyor suits both sides, or whether each owner wants their own surveyor.
- Build Party Wall fees and a realistic notice-to-award timescale into your winter building programme.
- Check planning permission and Building Regulations requirements separately; the Party Wall Act does not replace either.
FAQ
Does Stamp Duty staying unchanged in Budget 2026 affect Party Wall law? No. Stamp Duty is a tax on property purchases. The Party Wall etc. Act 1996 is separate legislation governing building work near boundaries. The link is behavioural: higher moving costs are pushing more households towards extending, which increases Party Wall activity.
Do I need a Party Wall notice for internal work that does not touch the party wall? Often not, but loft conversions commonly involve beams bearing onto the party wall, which does trigger the Act. Check with a chartered surveyor before assuming your scheme is exempt.
Can my neighbour refuse to let me extend? A neighbour cannot block lawful works outright, but they can dissent to a notice, which moves the matter to a formal award process under the Act rather than stopping the project.
How long before starting works should I serve notice? At least two months for Section 2 works to a party wall, and at least one month for Section 1 and Section 6 notices, measured from the date of service, not the date you plan to start.
Is a schedule of condition a legal requirement? It is not mandatory under the Act, but it is standard practice and strongly advisable, particularly for basement and excavation projects.
Conclusion
Budget 2026 left Stamp Duty where it was, mortgage rates remain elevated, and Zoopla’s October data shows a London sales market losing momentum. For a growing number of households, the extend or move decision is settling on “extend” now that Stamp Duty remains unchanged in Budget 2026. That shift brings Party Wall obligations into sharp focus for anyone planning a loft conversion, rear extension or basement this winter. Serve notices correctly, commission a schedule of condition, and build realistic timescales and fees into your project before the first digger arrives.
.cg-pw-wrap{font-family:Arial,sans-serif;max-width:600px;margin:0 auto;border:1px solid #ccc;border-radius:8px;padding:16px;background:#fafafa} .cg-pw-wrap h3{margin-top:0;color:#1a3c5e;font-size:18px} .cg-pw-wrap label{display:block;font-weight:bold;margin:10px 0 4px;font-size:14px} .cg-pw-wrap select{width:100%;padding:8px;border-radius:4px;border:1px solid #999;font-size:14px} .cg-pw-result{margin-top:14px;padding:12px;background:#fff;border-left:4px solid #1a3c5e;border-radius:4px;font-size:14px;line-height:1.5} .cg-pw-result strong{color:#1a3c5e}Party Wall Notice Finder
Loft conversion with steel beams Rear extension (new foundations) Basement or deep excavation New wall on the boundary lineTypical notice period: “+d.notice+”
“+d.note+” Always confirm with a chartered surveyor before serving notice.”; } document.getElementById(‘cg-work’).addEventListener(‘change’,cgUpdate); cgUpdate();