Is a Granny Annexe Cheaper Than Moving House in 2026? (UK)
For many UK families, building a granny annexe is cheaper than moving to a larger home. A granny annexe typically costs £40,000–£100,000, while the true cost of moving — stamp duty, estate-agent and legal fees, removals and the price gap to a bigger property — frequently adds up to more. Here is the full 2026 side-by-side comparison, plus the cases where moving still makes more sense.
The true cost of moving vs building an annexe (2026)
The headline price of a bigger house is only part of the story. Moving in 2026 also means stamp duty, estate-agent fees (typically 1–3%), legal and conveyancing fees, surveys, removals and often a sizeable price gap to the larger property. Add it up and the cost of trading up frequently runs to tens of thousands of pounds before you factor in the upheaval.
A granny annexe usually costs £40,000–£70,000 for a prefab or modular build and £80,000–£100,000+ for a larger bespoke masonry annexe, including groundworks and fit-out. Crucially, there is no stamp duty on building in your own garden, and you keep your home, your area and your equity.
Where the savings come from
The biggest single saving is usually stamp duty avoided plus the price gap you would pay to buy a larger home. On top of that you skip agent fees, most legal costs and the disruption of relocating. For multigenerational families, an annexe also keeps relatives close while preserving everyone's independence.
When moving still wins
An annexe is not always the answer. Moving can be the better choice if your garden is too small, if local planning restrictions are tight, if you actually need to change area (schools, work, accessibility), or if the annexe would over-develop the plot and hurt resale value. Always weigh the long-term plan, not just the upfront sums.
How to decide
1. Total the real cost of moving
Add stamp duty, agent fees, legal fees, removals and the price gap to a larger home for the true cost of moving.
2. Price up an annexe
Get quotes for a prefab or bespoke annexe sized to your needs, including groundworks, utilities and fit-out.
3. Check planning and council tax
Confirm whether the annexe is permitted development or needs planning permission, and how it affects council-tax banding.
4. Compare and decide
Weigh the all-in annexe cost against the all-in cost of moving, factoring in lifestyle, proximity to family and long-term value.
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