3rd September 2026
For years, the answer to a familiar housing problem has seemed fairly straightforward. If your house is too small, move to a bigger one.
Need another bedroom? Move.
Want a bigger kitchen and living room? Move.
Working from home and need an office? Move.
The trouble is that moving house has become an increasingly expensive way of solving what may actually be a relatively simple problem. And with mortgage rates still capable of moving upwards, it may be time for some homeowners to dust off an old idea that has perhaps been overlooked for too long.
Instead of moving, build.
It will not work for everybody, but for someone who already owns a house in a location they like and has enough land around it, extending the existing property could make considerably more financial sense than selling up and taking on a much larger mortgage.
The calculation has changed.
The Bank of England's Bank Rate currently stands at 3.75%, although three members of its Monetary Policy Committee voted in July for an increase to 4%. The Bank has also warned that higher and volatile energy prices could push inflation higher again later this year.
That matters because mortgage rates do not have to reach the levels seen a few years ago for borrowing an extra £50,000, £75,000 or £100,000 to become a significant long-term commitment.
The Bank says around five million households are projected to see their mortgage repayments increase by the end of 2028 compared with the situation before the recent energy shock. For the typical owner-occupier coming off a fixed-rate deal during the next two years, repayments are projected to be around £45 a month higher than previously expected.
So perhaps the question homeowners should be asking is not simply, "How much bigger a house can we afford?"
It should be, "Do we actually need to buy another house?"
The old calculation
Imagine a family owns a house worth £250,000.
It has served them well, but the family has grown and they would really like another bedroom, a larger kitchen or perhaps a proper home office.
They find a house for £350,000.
At first glance, it might appear that they only need another £100,000 of borrowing.
But that is not the full cost.
There are legal costs, estate-agent fees, removal costs and potentially repairs or improvements to the new property. In Scotland there may also be Land and Buildings Transaction Tax.
Revenue Scotland's latest figures demonstrate just how substantial the tax collected on residential transactions remains. In July 2026, residential LBTT excluding the Additional Dwelling Supplement raised £52.9 million, while the Additional Dwelling Supplement raised a further £26.6 million.
The homeowner has therefore not simply bought another £100,000 of space.
They have entered another financial transaction involving tens of thousands of pounds and, most importantly, potentially taken on a much larger mortgage.
And that mortgage continues to cost money year after year.
What if the house could simply be made bigger?
Now consider the alternative.
Suppose the existing house has enough garden or other usable space for an extension.
The homeowner might decide to build an additional bedroom, bathroom, office or larger living area instead.
The cost will depend enormously on the size and specification of the project, the site, access, foundations, services and local construction costs. There is no universal figure that can be applied to every extension.
But suppose, simply as an illustration, that the work costs £70,000.
That is a lot of money.
Yet it is still very different from selling a £250,000 house and buying a £350,000 one.
The homeowner has not had to find another property. They have not had to move. They have not paid the costs associated with selling and buying. And they may not have had to increase their mortgage by £100,000.
Better still, if the household can save towards the project and pay a substantial part of the cost from its own resources, it may be possible to create the additional space without adding a large new monthly mortgage commitment at all.
That changes the whole equation.
Saving instead of borrowing
There is an important psychological difference here.
We have become accustomed to thinking about housing in terms of what the bank will lend us.
If the bank says we can borrow another £100,000, it is tempting to think that a £100,000 more expensive house is therefore affordable.
But affordable to borrow is not necessarily the same thing as affordable to own.
A household that can save £500 a month may be able to accumulate £6,000 a year towards an extension. It might take several years, but the end result could be additional living space without the household taking on a large new mortgage.
There is no guarantee that building will be cheaper than moving. Construction costs can rise, projects can encounter unexpected problems and a badly designed extension can be poor value.
But the point is that the calculation deserves to be made rather than assuming that moving is automatically the answer.
There is another advantage
There is something else that can easily get lost in the house-moving calculation.
You already know your existing home.
You know the neighbours. You know the area. You know how long it takes to get to work, school, the shops or the coast. You know which rooms get the afternoon sun and where the wind comes from.
You may have spent years making the house your own.
Moving because you need another bedroom seems a rather drastic solution if the problem can be solved by building another bedroom.
This may be particularly relevant in rural Scotland, where a house may sit on a relatively generous plot compared with properties in larger towns and cities.
A family in Caithness, for example, may have a house with enough land to accommodate an extension but may never have seriously considered the possibility.
The house may have been built when the family was smaller. The children may have arrived later. A spare bedroom may have become an office. A garage may have become storage. Suddenly the house feels too small.
The instinct is to look at the property market.
Perhaps it should sometimes be to look at the garden.
It could also help local businesses
There is a wider economic argument here.
If more homeowners decide to improve rather than move, the money does not disappear from the housing economy.
It moves into construction.
Builders, joiners, electricians, plumbers, plasterers, roofers, heating engineers, architects and other trades can all benefit from domestic improvement work.
That could be particularly important at a time when there is already concern about the availability of skilled construction workers in rural areas.
An extension is therefore not simply a private household decision. A significant increase in home improvement work could create demand for exactly the sort of local trades that rural communities need to retain.
There is also an environmental argument.
Extending an existing house is not automatically environmentally superior. Construction itself uses materials and energy.
But where a family can adapt a house they already own rather than demolishing, selling, moving and undertaking major work on another property, there can be an obvious attraction in making better use of the existing building.
But there is a trap
The answer should not become another simplistic piece of financial advice saying that everybody should extend instead of moving.
Sometimes moving really is the better option.
The location may no longer work. The house may have fundamental problems. The extension required might be so large that it becomes disproportionately expensive. Planning restrictions may prevent the work. Or the finished property might not be suitable for the family's longer-term needs.
And homeowners should remember that the cost of an extension is not necessarily recovered pound-for-pound in the eventual value of the house.
Spending £80,000 does not guarantee that the property will be worth £80,000 more.
The financial case therefore needs to consider the value of the additional space to the people actually living there, rather than treating the extension purely as an investment.
That is an important distinction.
The question homeowners should be asking
Perhaps the biggest change is that people need to stop thinking about the choice as simply small house versus bigger house.
There is a third option.
The house you already own can sometimes become the bigger house.
And in an environment where mortgage rates remain uncertain, that deserves much more consideration.
The Bank of England has already reported weakness in housing market activity, with mortgage approvals for house purchase falling sharply in May and lenders expecting demand for secured lending for house purchases to weaken further.
That does not mean the housing market is about to collapse.
It does suggest, however, that households are becoming more cautious about taking on major housing commitments.
Perhaps that caution will encourage a change in behaviour.
Instead of asking how much more they can borrow, homeowners may start asking how much more space they can create without borrowing.
For somebody sitting in a perfectly good house with enough land around it, that could be a very different calculation.
And it might lead to a surprisingly simple conclusion.
Don't move. Build.
Sometimes the cheapest way to get a bigger house is not to buy one.