The cost of a garden annex in Sussex typically starts from £60,000 inc VAT, rising past £110,000 depending on size, specification and site conditions. The final figure depends on factors including the size of the annex, the internal specification, and what a particular garden needs in terms of groundworks and access. We provide a confirmed, itemised quote following a site visit, so homeowners know exactly what they are paying for before making any commitment.
What affects the cost of a garden annex?
There is no single price that applies to every garden annex, because no two projects are quite the same. A handful of factors consistently shape the final figure, and understanding them upfront makes the whole process far easier to plan around.
Size is the most obvious driver. A compact studio annex naturally costs less than a two-bedroom L-shape annex, simply because there is more structure, more services and more finishing involved. Our annex range covers everything from studio annexes through to larger, multi-room layouts, so the starting point depends largely on how much space a family actually needs.
Specification matters just as much as size. A kitchen and bathroom can be finished to a wide range of standards, and the fittings, worktops and sanitaryware chosen will move the price accordingly. The same applies to windows, doors and internal finishes.
Site conditions play a real role too. A flat, accessible garden with straightforward drainage routes is usually more cost-effective to build on than a sloping plot, a garden with restricted access, or one where existing drains sit some distance from the proposed annex position. We cover exactly what this involves in our guide to garden annex groundworks and foundations.
This is exactly why we look at every site individually. A period property in Lewes with a compact, walled garden presents very different access considerations to a larger plot in Petersfield or a new-build in Tunbridge Wells. Coastal gardens around Brighton and Hove can bring their own ground conditions to plan around, while homes in and around Guildford or Winchester often have more space to work with but longer drainage runs back to the main house. None of this changes the starting price of the annex itself, but it is exactly the kind of detail a site visit is designed to capture.
Taken together, these factors mean that two annexes of a similar size can end up at noticeably different prices, depending on specification and site. It is exactly why we treat every quote as something to be confirmed for the individual property, rather than a fixed number applied across the board.
What is our price range for a garden annex?
Our annexes start from £60,000 inc VAT for a studio annex, with the price increasing from there depending on size and specification. Larger and more heavily specified annexes, including multi-room and pitched roof layouts, sit at the higher end of what we build.
We do not publish a single fixed price list, because the accurate figure for any project depends on the combination of size, specification and site conditions covered above. What we do provide is a confirmed, itemised quote following an initial site visit, so homeowners are working from a real number rather than an estimate that might change later. You can browse the full range of annex sizes and layouts on our annexes page as a starting point for thinking about what might suit your garden and your family.
What’s included in the price?
One of the most common questions we hear is what actually sits within the headline figure, and it is a fair one to ask given the scale of the investment.
Our price includes ground screw foundations rather than a large concrete base, the full installation of the annex itself, a complete kitchen and bathroom specification fitted as standard, and a 10-year manufacturer’s guarantee giving homeowners long-term reassurance on the build itself. Planning is managed separately through our £1,500 planning package, covered in full below.
In practical terms, this means the figure we quote is designed to reflect a genuinely finished, liveable space rather than a shell that still needs significant additional spend to become functional. That is a deliberate part of how we price projects, and it is one of the reasons families across Sussex, Surrey, Kent and Hampshire come to us for a straightforward, considered build rather than piecing one together themselves.
What can add to the cost?
Groundworks are the most significant of these, and they are always priced separately from the annex build itself. As part of the process, we arrange a full professional site survey, so the exact groundworks cost is confirmed based on your specific site, including drainage routes, ground conditions and access. We explain exactly what this involves, and why it is rarely as disruptive as homeowners expect, in our guide to garden annex groundworks and foundations.
Access requirements can also affect cost. A garden with straightforward access for machinery and materials is generally more straightforward to build on than one with restricted access, narrow side passages or limited space to manoeuvre.
Post-build landscaping is another area some families choose to invest in separately, whether that is reinstating a lawn, adding new planting around the annex, or creating a wider seating area. This sits outside the core annex build and is very much down to individual preference.
We keep these costs clearly separate from the annex price itself, confirmed via a professional survey and site visit, so homeowners can see exactly what they are paying for at each stage rather than working from a single blended figure.
How does our pricing compare to the wider market?
Garden annex pricing varies considerably across the UK. Based on 176 published prices, UK garden annexes typically cost between £52,000-£155,000 or more (The Garden Room Guide, April 2026), reflecting the wide range of sizes, specifications and build qualities available.
Within that range, we sit towards the premium end, and that reflects the way we build. Full kitchen and bathroom specification as standard and a 10-year guarantee are not add-ons in our approach, they are part of the core offering from the outset. Planning is managed with the same level of care, though as a distinct part of the process rather than folded into the build price. For many families, an annex is also being weighed up against long-term alternatives such as residential care, where fees typically run to £45,000-£80,000 or more per year. We look at that comparison in more detail in our guide to garden annexes versus care home costs, which is worth bearing in mind as part of the wider picture when thinking about value over time.
What we hear consistently from families is that clarity matters as much as the number itself. A confirmed, itemised quote following a site visit means there is nothing to second-guess later in the process.
How much does planning cost for a garden annex?
Planning is one part of the process homeowners often assume will bring unexpected costs, and we manage it as a single, transparent package rather than a series of separate charges.
Our planning package is £1,500 inc VAT and covers the full process end to end, including architectural drawings, the relevant application or applications, and day-to-day contact with the local council. Our guide to planning permission for garden annexes explains how this works in more detail, including the different routes a project might take depending on the structure being built.
Because this is included as a fixed package rather than billed as work progresses, it is one of the more predictable elements of the overall cost, even before a site visit has taken place.
If you have any questions about your own project before getting in touch, our team is always happy to talk through the detail. You can contact us directly, or read on for answers to some of the questions we hear most often.
Frequently Asked Questions
How much does a garden annex cost in Sussex?
Garden annexes typically start from £60,000 inc VAT, rising depending on size and specification. A confirmed, itemised cost is provided following a site visit, once the specific requirements of the project are understood.
Does the annex price include planning permission?
No, planning is managed as a separate £1,500 inc VAT package. It covers drawings, the relevant application, and liaison with the local council from start to finish, and is confirmed as part of your overall proposal alongside the annex build cost.
Are groundworks included in the annex price?
No. Groundworks are always priced separately from the annex build. We arrange a full professional site survey as part of the process, so the exact cost is confirmed based on your garden’s drainage routes, ground conditions and access.
How does a garden annex compare in cost to a care home?
Care home fees typically run to £45,000-£80,000 or more per year, so the cost of an annex is often weighed against several years of ongoing fees. This is a common consideration for families exploring multigenerational living, and one we look at in more detail in our recent article about costs and investment.
What is included in the standard annex specification?
Our annexes include a full kitchen and bathroom specification, ground screw foundations, complete installation and a 10-year manufacturer’s guarantee, all included as standard rather than offered as upgrades.
Ready to understand what your project would cost?
Every garden is different, which is why the most useful next step is a straightforward conversation followed by a site visit. From there, we provide a confirmed, itemised quote so you know exactly what your project would involve before making any decision.
If you would like to see how other families across Sussex, Surrey, Kent and Hampshire have approached their own projects, take a look at our customer stories. Or get in touch with the team for an initial conversation. It is always free, honest and without obligation.