Is it better to move house or extend? How to decide

Extensions · Planning your project

Should you move house or extend? How to compare the two, what moving costs in stamp duty at today’s rates, and how to find out what your house can take before you decide.

Last updated: 2 November 2026 · Reviewed by Graham Sproul RIBA, Design & Operations Director

The figures here are approximate and meant to give you an idea, not a quote. Every house and brief is different, so your costs and programme will depend on your project.

Move house or extend: how to decide

If you’ve outgrown your house but not your street, start from there. When the area and the schools still suit you, extending keeps them, and the question becomes whether your house can give you the rooms you need at a cost and level of disruption you can live with. If you need to be somewhere else, no extension solves that.

Factor	Points towards extending	Points towards moving
Location	You want to stay in the area, near schools and family	You need a different area, or more outside space than your plot has
What the house can take	Room to extend at the back, side or into the loft, and a realistic planning route	Planning constraints or the plot rule out the space you need
Money	The build cost buys space; nothing is spent on transaction taxes	The house you want costs less, all in, than building the space
Disruption	You can live with months of building work, or move out during it	You need the space quickly, with no building work
Result	A layout designed around how you live	A house someone else designed, which may still need work

What moving costs: stamp duty at today’s rates

Stamp Duty Land Tax is the cost of moving you can work out exactly, because HMRC publishes the rates. For a home you’ll live in, these are the residential rates that apply from 1 April 2025, checked on GOV.UK on 30 October 2026.

Part of the price	Rate
Up to £125,000	0%
£125,001 to £250,000	2%
£250,001 to £925,000	5%
£925,001 to £1.5 million	10%
Above £1.5 million	12%

On top of stamp duty come estate agent’s fees, conveyancing, a survey, mortgage fees and removals, and none of them buys any extra space.

Worked example: the stamp duty on moving up

Say you sell a house for £850,000 and buy one for £1.1 million to get the extra bedroom and a bigger kitchen. Here is the stamp duty on the purchase, band by band.

Band	Amount in the band	Rate	Tax
Up to £125,000	£125,000	0%	£0
£125,001 to £250,000	£125,000	2%	£2,500
£250,001 to £925,000	£675,000	5%	£33,750
£925,001 to £1.1 million	£175,000	10%	£17,500
Total	£1,100,000		£53,750

The £53,750 is 21.5% of the £250,000 difference between the two prices, spent before agents, solicitors, surveys and removals. At other prices, the same rates give £30,000 on an £800,000 home, £43,750 on £1 million and £68,750 on £1.25 million.

What extending costs, and what it gives you

An extension’s cost depends on its size and how much of the existing house changes with it. Our house extension cost guide sets out prices per square metre, and if the whole house needs work, our renovation cost per m² guide covers that. Compare like with like: the cost of the space you need, built, against the stamp duty and other costs of moving to a house that already has it, plus anything that house would need doing.

Extending also has costs that are easy to forget. There are fees for the architect and engineer, planning and Building Regulations fees, party wall costs if you share walls, and possibly rent if you move out during the build. Against that, the money goes into your own house, and the layout is designed around how you live.

Two of those costs are easy to put numbers on early. A householder planning application in England costs £548 from 1 April 2026, and a new national fee schedule proposed from around 8 December 2026, subject to Parliament, would take it to about £575. If you share walls, party wall notices go to each adjoining owner, and our fee proposals suggest allowing about £1,000 per neighbour; our party wall guide explains when notices are needed. Time is the other cost. We advise clients to allow about three months for a planning decision, and on simpler schemes we can start the Building Regulations drawings while it is pending, at the client’s risk, so the wait doesn’t hold up the tender. If you need the space by a fixed date, such as before a baby arrives or a child starts school, set that date against the programme before you choose.

What your house can take

Before you can compare the two, you need to know whether extending can give you the space at all. That comes down to planning and the house itself. Some extensions can be built under permitted development, and others need planning permission; our guide to planning permission vs permitted development explains how to tell which applies. A conservation area or listing narrows the options. Check the planning history too: some houses have had their permitted development rights removed by a condition on an earlier permission, and the council’s online planning register shows the past applications and decisions for your address, so you can see what has been approved on the house and on its neighbours.

Then look at where the space can come from. A rear or side extension usually adds kitchen and living space, and a loft usually adds a bedroom and bathroom. A basement adds space without changing the garden or roofline, and reworking the existing rooms can find space without adding any. Our comparison of basement vs loft vs extension sets them side by side.

Thinking about how long you’ll stay

The English Housing Survey 2023-24 puts the average time owner-occupiers have lived in their home at 17.2 years, and 23.8 years for those who own outright. A move made for today’s family will often be lived in for long after the children have left. If you’re unlikely to move again for a long time, design for the space you’ll want in 15 years as well as the space you need now.

What a loft conversion adds

A loft conversion usually adds a bedroom and a bathroom. What that is worth depends on your street, so ask a local estate agent to price it, then set it against the build cost in our London loft conversion guide.

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