Double Storey Extension Cost UK 2025
A double storey extension is one of the hottest options when it comes to creating space, comfort, and long-term value to your home as a homeowner in the UK. Whether it be an additional bedroom, a bigger kitchen or even a home office, a two storey addition changes the way you live. Yet, it is crucial to know how much an extension can cost in the UK in 2025, especially considering the double storey house extension costs. Whether it is prices to use average prices to the factors affecting average prices, this guide will assist you in making a well-informed choice and may save your money in the process.
How Much Does a Double Storey Extension Cost in the UK?
The first question in the mind of every homeowner should be, how much does a double storey extension cost? The reality is that there is no set price due to the many factors that come into consideration including size, location, workmanship of finish on the building and the intricacy of the construct. However, as of 2025, the double storey extension cost in the UK typically ranges between £1,800 to £3,000 per square metre. Therefore, to extend your home by 40m2 it may cost you as little as £72,000 or as much as £120,000 depending on the design and material you select.
It is also worth bearing in mind that a double storey extension should be vastly more attractive, taken on a per-square-metre, basis than a single storey extension. This is since the addition of the foundations and roofing have already been completed, it is relatively more efficient to build upwards.
Average Cost of a Double Storey Extension in the UK
Taking averages over 2025 the average spending of homeowners is between £80,000-£120,000 on an average double storey rear or side extension. London and the South East are more likely to have a higher price attributable to labour and material prices and the rest of the UK would have an average slightly less.
This investment can easily equate to a dramatic increase in property value with the addition of a double storey extension regularly contributing more money to the end value of a home than the overall cost of building it. It is still one of the financially viable options among the families who might want to add and not relocate.
Key Factors That Influence Double Extension Costs
The double storey extension cost is never just about size. There are a number of considerations that influence the amount of money you end up with and being conscious of these can make it easier to make a more useful budget.
One of the largest factors here is location as a city project in London, Manchester or Birmingham is likely to be more expensive than the rural or suburban. The materials used also count: selecting high-end finishes like aluminium bi-fold doors, underfloor heating, or tailor-made joinery will increase the price in contrast to the usual elements.
The other important factor is the complexity of the design. The utilitarian and squarish addition is simple to construct, in comparison to the one that alters the structural elements, accommodates awkward combinations of roofs and needs steel members. If you’re removing load-bearing walls, adding extra bathrooms, or installing large glazing sections, expect the overall double storey extension cost UK homeowners face to rise.
Lastly, do not overlook planning and fees by professionals. There are further costs involved at the architect stage, structural engineers, planning applications and building regulations approval and this will contribute to the overall total and can comprise 10-15 percent of the total project cost.
Double Storey Side and Rear Extension Cost Breakdown
Your extension position, side count or rear also makes a difference. The rear extension that often doubles as a kitchen extension and addition of a bedroom overhead is typically seen as a little cheaper compared to a side extension which could be more structurally involved particularly where it is awkwardly linked with existing plans.
A double storey rear extension cost is anticipated to average between £80,000 and £100,000 and the auxiliary figure of costs for a double storey side extension is likely to be between £90,000 and £120,000, according to site conditions. When you combine a side and a rear extension, to create a wraparound, the price logically goes up but the result provides the most transformation of your property.
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Extension Cost per m²: What You Should Expect
Dividing the costs in terms of square metre assists in comparing the options in a more open manner. The average cost of extension per m2 of the double storey projects is between 1,800 and 3,000 in 2025 as noted earlier. The lower figure of this scale is often used in reference to less complex builds with standard finishes whereas the upper scale is used in reference to high-range materials, complicated arrangement and prominent urban real estate.
This square metre pound calculation comes also in handy when deciding to extend or move house. As an example, in much of the UK the cost of extension per square metre can still be less than the total cost of selling, house moving and buying a larger house.
