Should I extend my house or sell and move?

This is one of the most common decisions a homeowner puts off, usually because both options look expensive and neither feels obviously right. It is a solvable question. Once the two costs sit side by side and you know what your home is worth now, the answer is usually clearer than it feels.

What does an extension actually cost in 2026?

An extension is new floor space added to an existing home, built either outwards, upwards into the roof, or by converting space you already own such as a garage. Build costs are quoted per square metre, and the total lands well above the build figure once professional fees and VAT go on top.

Then come the costs that rarely appear in the builder's quote. Budget for them from the start rather than meeting them halfway through.

What does moving actually cost?

Moving costs are spread across two transactions, which is why people underestimate them. You pay to sell and you pay to buy, and for most home movers the tax is the single largest line.

Stamp duty land tax is a tax paid by the buyer on property purchases in England and Northern Ireland. A home mover replacing their main residence pays the standard rates: nothing up to £125,000, 2% on the slice from £125,001 to £250,000, and 5% from £250,001 to £925,000. On a £292,000 purchase that comes to £4,600.

Add those together and a typical move on an averagely priced home lands in five figures before you have bought a single tin of paint. The gap narrows fast when the extension you are considering runs past £50,000.

Will an extension add back more than it costs?

Sometimes, and the pattern is well documented. Nationwide's research published on 15 October 2025 found that a loft conversion or extension adding a double bedroom and a bathroom can add as much as 24% to the value of a three-bedroom, one-bathroom house, and that adding a double bedroom to a two-bedroom house can add 13%.

The most useful figure in that research is the plainest one: roughly 5% more value for every 10% of extra floor space. It gives you a number to test your own plan against.

• On a £350,000 home, a 10% increase in floor space points to around £17,500 of extra value. A 20 square metre extension at £40,000 to £56,000 would not pay for itself on value alone.
• Adding a bedroom is where the money is, because it moves the home into a different search bracket. Extra square metres in an existing room rarely do.
• A second bathroom added around 4% in the same research, which is worth having but rarely worth borrowing for on its own.
• The average spend on home improvements in that research was around £52,000, and 4% of homeowners said they regretted the work.

The limit that catches people is the ceiling price. The ceiling price is the most that buyers will pay for any home on a given street, whatever its size or condition. Push your home above it and the extra space stops converting into value, because the buyer who wants that much house will look at a road where every home is that size.

Extending works when it buys you the space you actually lack. It rarely works as an investment on a street that has already found its ceiling.

How do I decide between extending and moving?

1. 1. Name the problem in one sentence

   Write down what is actually wrong with the house. If the answer is a bedroom short, extending can fix it. If the answer is the area, the commute, the schools or the garden, no amount of building work will.

2. 2. Get your home valued before you plan anything

   Every part of this maths starts from what your home is worth today. Get more than one figure from local agents so you are working from a range rather than one opinion, and do it before you commit to either path.

3. 3. Find your street's ceiling price

   Look at what the largest, most improved homes on your street and the streets either side actually sold for. That is the practical limit on what extending can return, and it takes an evening to establish.

4. 4. Price the extension properly

   Take the build quote, add the professional fees, the planning and building control costs, VAT, and a contingency of at least 10%. Compare that total, not the builder's headline figure, against everything else.

5. 5. Price the move properly

   Add the stamp duty on the home you would buy, your agent fee, two sets of conveyancing, removals and the small costs. This is the real number the extension is competing against.

6. 6. Check what you can borrow either way

   Ask your lender what a further advance on your current mortgage would cost, and what a larger mortgage on a bigger home would cost. Compare the monthly payments, not the totals, because that is what you actually live with.

7. 7. Factor in the upheaval honestly

   A significant extension means months of building work while you live in the house, and the risk of overrun. A move means a slower process than most people expect. Neither is quick, so choose the one whose upheaval you can live with.

8. 8. Decide, then commit

   Half-measures cost the most. Extending badly to avoid moving, or moving in a hurry to avoid building, both end up more expensive than the decision you delayed.

Extending or moving: the pros and cons side by side

Common questions about extending versus moving

ValuQ gives UK homeowners free, side-by-side property valuations from competing local estate agents, and it is free for homeowners, always. If you are weighing an extension against a move, knowing what your home is worth now, from several agents rather than one, is the number both sides of the decision rest on.