Extend or Move? The Real Cost Comparison for UK Homeowners in 2026

It's one of the biggest decisions a UK homeowner faces: do you extend the home you have, or sell up and buy somewhere bigger? The emotional pull often points towards a fresh start, but the financial case almost always favours extending. Here's the full breakdown to help you decide.

The True Cost of Moving

Moving house involves a long list of fees that many homeowners underestimate. Here's what it actually costs to sell a £300,000 home and buy at £400,000:

| Fee | Typical Cost | |---|---| | Estate agent (1.5% of sale price) | £4,500 | | Solicitor / conveyancer (sale + purchase) | £2,000–£3,500 | | Stamp duty (on £400,000 purchase) | £7,500 | | Survey (RICS Level 2 or 3) | £500–£1,500 | | Mortgage arrangement fee | £500–£1,500 | | Removal company | £1,000–£2,500 | | EPC certificate | £60–£120 | | Repairs, cleaning, and decoration (new home) | £1,000–£5,000 | | Redirected mail, new curtains, and incidentals | £500–£1,500 | | Total | £17,500–£27,000 |

And that's before the higher mortgage payments. If you're moving from a £300,000 home to a £400,000 home, you're adding £100,000 to your mortgage. At 4.5% over 25 years, that's an extra £555 per month — or £166,500 in total repayments.

Stamp Duty at Different Price Points

| Purchase Price | Stamp Duty | Notes | |---|---|---| | £250,000 | £0 | Nil-rate band | | £300,000 | £2,500 | 5% on £50k above threshold | | £400,000 | £7,500 | | | £500,000 | £12,500 | | | £600,000 | £17,500 | | | £750,000 | £25,000 | | | £1,000,000 | £41,250 | 10% band kicks in at £925k |

Stamp duty is a pure sunk cost — you get nothing tangible in return. That £7,500–£25,000 could fund a significant portion of an extension instead.

The True Cost of Extending

An extension's cost depends on the type, size, and your location. Here's the all-in cost including professional fees, Building Control, and making good:

| Extension Type | Typical All-In Cost | Space Added | |---|---|---| | Garage conversion | £12,000–£22,000 | 15–18m² | | Loft conversion (dormer) | £38,000–£60,000 | 20–30m² | | Single-storey rear (20m²) | £40,000–£65,000 | 20m² | | Kitchen extension (25m²) | £50,000–£85,000 | 25m² | | Double-storey rear (20m² footprint) | £60,000–£100,000 | 40m² |

Use our free quote calculator for a personalised estimate based on your location and specification.

The Financial Comparison

Let's compare a real scenario. A family in a 3-bed semi worth £300,000 needs more space — either a 4th bedroom and larger kitchen.

Option A: Move to a 4-Bed

| Item | Cost | |---|---| | Purchase price of 4-bed | £400,000 | | Minus sale of current home | −£300,000 | | Net price difference | £100,000 | | Estate agent fees | £4,500 | | Solicitor (both transactions) | £3,000 | | Stamp duty | £7,500 | | Survey + mortgage fees | £1,500 | | Removals | £1,500 | | Decoration and repairs (new home) | £3,000 | | Total cost to move | £121,000 |

Option B: Extend

| Item | Cost | |---|---| | Loft conversion (new bedroom + en-suite) | £45,000 | | Kitchen extension (20m² open-plan) | £55,000 | | Hidden costs + contingency | £12,000 | | Total cost to extend | £112,000 | | Estimated value added to property | £60,000–£90,000 | | Net cost after value gain | £22,000–£52,000 |

The extension delivers equivalent space for a similar upfront cost — but you also gain £60,000–£90,000 in property value. Moving creates zero equity; the fees are a dead cost.

The Decision Framework

Extend When...

• You love your location — school catchment, commute, community
• Your home has room to grow — garden space, loft potential, garage to convert
• The street supports the value — comparable extended homes sell for enough to justify the investment
• You want to build equity — extensions add value; moving fees don't
• You want to avoid chain risk — no failed sales, no gazumping, no chain collapses

Move When...

• You need a different area — new job, schools, downsizing, lifestyle change
• Your plot is maxed out — tiny garden, no loft potential, already extended
• The ceiling price limits returns — if every house on the street sells for £280k–£320k, a £100k extension won't take yours to £420k
• The home has fundamental problems — flood risk, structural issues, poor orientation, noise
• You want a bigger garden — extensions give more house, not more land

Hidden Advantages of Extending

1. No Chain

You're not relying on a chain of buyers and sellers. An extension project is entirely within your control — no gazumping, no delays waiting for someone else's mortgage offer.

2. You Keep Your Neighbourhood

Schools, GP, friends, local shops, commute route — all unchanged. The value of an established life in a community is hard to quantify but very real.

3. You Design Exactly What You Want

A new-to-you house is a compromise — someone else's layout, kitchen, and decoration. An extension is built to your specification.

4. No Stamp Duty

Every pound saved on stamp duty is a pound that could go into your build budget.

5. Staged Approach

You can extend in phases — a loft conversion now, a kitchen extension in 2–3 years — spreading the cost and disruption.

When the Numbers Are Close

If the financial comparison is tight, consider these tiebreakers:

| Factor | Favours Extending | Favours Moving | |---|---|---| | Disruption tolerance | Medium (stay in home during build) | High (moving is a one-off event) | | Time to enjoy the space | 6–12 months to build | Available immediately after move | | Financial risk | Build costs can overrun (budget 10–15% contingency) | Market risk (property could lose value) | | Emotional attachment | Want to stay | Ready for a change | | Family timing | School year, newborns — disruption is manageable | Gap between school years or before children |

How to Check the Ceiling Price

Before committing to a major extension, verify that your street supports the added value:

1. Check recent sales on your road — use the Land Registry's Price Paid data (free)
2. Look for extended comparable homes — what did a similar extended house sell for?
3. Get an estate agent's opinion — ask 2–3 local agents what your home would be worth with the proposed extension
4. Calculate the maximum — if the ceiling is £350k and your home is worth £300k, spending more than £50k on an extension risks overcapitalising

Next Steps

1. Run the numbers — cost out both scenarios using real figures for your area
2. Get an extension quote — our free calculator gives a detailed cost breakdown
3. Check comparable sales — what do extended homes on your street sell for?
4. Talk to a mortgage broker — compare the cost of a larger mortgage (moving) vs a smaller one (extending)
5. Read about financing your extension if borrowing
6. Understand which improvements add most value to prioritise the highest-ROI projects