Thinking About a Home Extension in Berkshire?

The decision to start a home extension rather than move is one that more Berkshire homeowners are making right now than at any point in recent memory. Stamp duty, moving costs, the disruption of uprooting a family — and a housing market that offers precious little step-up value in the local area — all push in the same direction.

If you need more space, building it where you are is increasingly the rational choice. The question is what kind of extension makes sense for your home, what it’s realistically going to cost, and what the process of getting it done actually looks like.

These aren’t simple questions, and the honest answer is that they vary considerably depending on your property, your plot, your ambitions, and the specification you choose. But there are patterns — types of extension that homeowners in Bracknell and the wider Berkshire area are choosing most often, cost ranges that reflect what builders are actually quoting in 2026, and decisions that tend to determine whether a project goes smoothly or becomes more complicated than it needed to be.

The single most popular home extension type in the area remains the rear single-storey extension — and it’s popular for good reason. Most semi-detached and detached homes in Bracknell and the surrounding towns have a rear garden with a clear run from the back of the house, which means there’s usually planning headroom and a logical direction to build.

A well-designed rear extension typically creates a significantly enlarged kitchen-diner, opens the house to the garden, and transforms the way a family uses their ground floor. Done well, it changes the character of the house.

Side-return extensions are gaining popularity among properties where a narrow side passage runs along the flank of the house — common in many of Berkshire’s older semi-detached streets. Infilling this passage and extending into it can add meaningful floor area without touching the rear garden, and the resulting space often creates the open-plan ground floor layout that buyers and homeowners alike are looking for.

Double-storey extensions — adding rooms on both ground and first floor in a single build — are a more significant undertaking but represent excellent value per square metre compared to two separate projects, and they’re increasingly the choice for families who know they need more space on both levels.

Build costs have shifted considerably in the past few years, and any figure from 2022 or 2023 should be treated with caution. In Berkshire in 2026, a realistic budget for a single-storey rear extension of around 20 square metres — finished to a good specification — typically falls in the range of £45,000 to £65,000.

This is a wide range because specification matters enormously: the choice of glazing, the quality of finishes, whether the kitchen needs to be reconfigured as part of the work, and what the existing structure requires by way of preparation all move the needle significantly.

A double-storey extension of similar footprint — adding both a ground-floor room and a bedroom or bathroom above — typically costs between £80,000 and £120,000, again depending heavily on specification. These figures include structural work, materials, labour, and a reasonable contingency, but they do not include architectural fees, planning application costs, or structural engineer’s reports, which should be factored in from the outset.

According to the Federation of Master Builders, whose members include Kiewlen Builders, getting multiple quotes from vetted, insured builders remains the most reliable way to arrive at an accurate budget for a specific project — national averages are a guide, not a guarantee.

One of the most common sources of confusion at the start of a home extension project is planning permission. Many extensions fall within permitted development rights — meaning they can be built without a formal planning application — but the rules have specific limits that are easy to accidentally exceed, and the consequences of building without the necessary permissions can be serious at point of sale.

As a general guide, a single-storey rear extension on a semi-detached or detached house can extend up to 4 metres beyond the original rear wall under permitted development (6 metres under the neighbour consultation scheme, subject to no objections). Side extensions, double-storey extensions, and extensions that take the building close to a boundary are more likely to require full planning permission.

Properties in conservation areas or those with an Article 4 direction in place have more restrictions still. The safest approach is always to confirm the position with your local planning authority or through a pre-application consultation before committing to a design — and a good builder or architect will flag these considerations as part of the early project conversation. Kiewlen Builders’ home extensions service includes guidance through this process from the outset.

Beyond the type of extension and the headline budget, a handful of decisions tend to define whether a project delivers the result homeowners are hoping for. The first is the relationship between the extension and the existing house — a well-designed extension should feel like it belongs, not like a box bolted onto the back.

This requires thought about roof form, materials, the positioning of glazing, and the transition between the old and new parts of the house. Getting an architect or experienced designer involved at an early stage, rather than working from a basic sketch, almost always produces a better outcome.

The second is contractor selection. An extension is a significant financial commitment and a significant disruption to daily life — and the quality of the builder you choose determines both how the project runs and how it finishes. Membership of the Federation of Master Builders provides a baseline of assurance: members are vetted, insured, and committed to a code of practice that offers recourse if things go wrong.

Beyond accreditation, visiting completed projects, speaking to previous clients, and ensuring that the quote is detailed enough to compare fairly with others are all steps that reduce risk and increase the likelihood of a project that lands as planned. The same applies to conversions and property refurbishments — the right builder makes the difference across every type of project.

A home extension is one of the most transformative investments a homeowner can make — in their daily comfort, their family’s quality of life, and the long-term value of their property.

Getting it right requires the right decisions at each stage: the right type of extension for the house and the plot, a realistic budget built on current costs rather than outdated estimates, the right approach to planning, and the right builder to bring it all together.

Kiewlen Builders is a family-run construction company based in Bracknell, working with homeowners across Berkshire on extensions, renovations, and a full range of building projects.

With over a decade of experience and membership of the Federation of Master Builders, we bring the craftsmanship and transparency that a project of this scale deserves. If you’re at the early stages of thinking through a home extension, we’d be glad to have a straightforward conversation about what’s possible. Get in touch with the Kiewlen team to get started.