How Much Does a House Extension Cost in Somerset?

If you are thinking about extending your home, one of the first questions is usually cost. The honest answer is that a house extension in Somerset can vary quite a lot depending on size, design, specification and the condition of the existing property. As a rough guide, many straightforward single-storey extensions might start from around £2,200 to £3,200 per square metre, while more complex or highly specified work can rise beyond that. For double-storey extensions, the cost per square metre can sometimes look more efficient overall, but the total budget is of course higher.

In Somerset, budgets are often shaped by the kind of home you are extending. Many homeowners live in a mix of Victorian terraces, period cottages, post-war houses and more modern estates, and each brings its own considerations. Older homes may need more structural care, extra insulation upgrades or careful detailing to blend old and new. Newer properties can be simpler in some respects, but access, drainage, layout changes and finishes still make a major difference to the final figure. If you are at the early stage, our house extension services page gives a useful overview of what is involved.

Typical extension cost ranges

As a rough guide, a modest rear extension for a kitchen, dining or family space might typically fall somewhere from £60,000 to £120,000, depending on scale and finish. A larger single-storey extension with more glazing, structural alterations and bespoke joinery could easily sit above that range. Double-storey extensions often begin from around £90,000 to £180,000 or more, particularly where the project includes bathrooms, utility rooms, extensive remodelling or upgraded heating systems. These are not fixed prices, just broad starting points for planning.

It is also worth remembering that build cost is only one part of the budget. Professional fees, structural engineering, planning or building regulations applications where needed, site surveys, kitchen costs, flooring, decorating, landscaping and VAT can all affect the overall spend. Homeowners are sometimes surprised by how much the internal fit-out influences the final number. A simple shell extension and a fully finished, ready-to-use living space can sit in very different budget brackets.

What pushes the cost up or down?

The biggest cost factors are usually size, complexity and specification. A simple rectangular extension with standard roof forms is generally more cost-effective than a design with large rooflights, lots of sliding glass, awkward ground conditions or major steelwork. If you are opening up the back of the house, relocating drains, moving a boiler, upgrading electrics or installing underfloor heating, the budget can rise quickly. On the other hand, a well-planned design that works efficiently with the existing structure can help keep costs under better control.

Materials and finishes matter too. Brickwork, roofing, windows and doors need to suit the house as well as the budget, and there can be a wide range in cost between good standard products and premium bespoke options. Inside, kitchens, utility rooms and bathrooms are usually among the largest variable costs. That is why early design decisions are so important: they help you understand where to invest, where to simplify and how to avoid expensive late changes.

Somerset projects can also be affected by practical site issues. Access can be straightforward on some suburban plots, but tighter village settings, sloping gardens or restricted parking can make a build more involved. Ground conditions may require additional foundation work, and older properties may reveal surprises once work begins. A sensible contingency is therefore important. Many homeowners allow a contingency of around 10% to 15% as a rough guide, especially for extensions to older homes.

Planning, regulations and timescales

Some house extensions may fall within permitted development rights, while others will need householder planning permission, and the position depends on the property and the proposal. Building regulations approval is typically required for extension work in any case. Because rules can vary and special situations such as listed buildings or conservation areas need extra care, it is always best to check the details with your local authority in Somerset before making firm assumptions. A design-and-build approach can help join up these early decisions with the budget from the outset. You can read more about that on our how we work page.

Time is another part of cost planning. A smaller, straightforward extension may take a few months on site, while a larger or more complex scheme can take longer, especially if it includes major alterations to the existing house. Good preparation usually saves money: clear drawings, thoughtful specifications and realistic allowances reduce the risk of delays, variations and rushed decisions. If you want a very early ballpark, our cost calculator can be a helpful starting point.

Getting better value from your budget

The best value does not always come from building the biggest extension. In many Somerset homes, careful layout changes can transform how the house feels without adding unnecessary square footage. A well-designed kitchen extension, for example, may combine dining, utility storage and better garden connection in one coherent space. Equally, if you are considering broader changes, it can make sense to think about the extension alongside renovation work rather than treating each decision separately. You can see the kind of thoughtful whole-home approach we take in a recent NOOR renovation in the area.

For many households, the most useful next step is not chasing a single headline price, but understanding the right budget range for their particular home and priorities. A realistic appraisal should look at the house, the brief, the likely construction approach and the level of finish you want. That is especially true across Somerset, where homes and sites vary so much from one setting to another. If you are looking for experienced builders in Somerset, it helps to choose a team that can guide both design and cost decisions clearly.

If you are exploring a house extension cost in Somerset and want practical, tailored advice, we would be happy to help. The best conversations start with your home, your goals and your likely budget range, so we can shape a proposal that feels right from the beginning. When you are ready, you can request a consultation.