how-to
How Do You Get a Quote for a Custom Annex?
Adrian Bennett · 30 October 2026
Last Updated: October 30, 2026
Quick Summary
To get a quote for a custom annex, gather your footprint, intended use, service needs, garden photos and budget, then book a site survey so the figure is confirmed in person. A credible custom annex quote is itemised and fixed-scope, covering design, groundworks, structure, glazing, electrics, insulation and finishing.
- Bespoke garden annex cost is driven by size, specification level, site access and groundwork demands.
- A phone quote is an estimate; a quote after a site inspection is far more reliable.
- Compare quotes on scope, not totals, checking breakdown, groundworks, electrics, guarantee and payment terms.
- Ask every provider what is excluded, what triggers a variation, and what happens if ground is worse than expected.
- Kent Bespoke Garden Rooms offers a 10-year structural guarantee and access to FCA-regulated finance options.
Table of Contents
- What a Custom Annex Quote Actually Covers
- What Drives Bespoke Garden Annex Cost
- Your Garden Annex Quote Checklist Before You Call
- Why a Garden Annex Site Survey Comes First
- Garden Annex Finance Options Explained
- How to Compare Quotes for a Custom Annex
- Request Your Free Custom Annex Quote
- Frequently Asked Questions
What a Custom Annex Quote Actually Covers
If you want to get a quote for custom annex, you need to know what you're actually being quoted for. A proper custom annex quote is an itemised, fixed-scope document covering design, groundworks, structure, glazing, electrics, insulation, finishing and any site-specific work, not a single lump sum scribbled on a business card.
At Kent Bespoke Garden Rooms™, we build bespoke garden rooms, offices and self-contained annexes, and the quotes that cause trouble are almost always the vague ones. A short figure with no breakdown tells you nothing about what happens when the ground turns out to be clay, or when the electrics need a longer run than expected. Below, we'll show you exactly what a credible quote should contain, what pushes the bespoke garden annex cost up or down, and how to compare two quotes fairly.
Most guides get this wrong. They treat the quote as the end of the process when it's really the start of a proper conversation about specification.
What Drives Bespoke Garden Annex Cost
Bespoke garden annex cost is driven by four things: size and footprint, specification level, site access, and how much groundwork the plot demands. Everything else, from cladding to glazing, is a dial you can turn up or down.
Size is the obvious lever. A single-room garden office and a self-contained annex with a bedroom, shower room and kitchenette are different projects entirely, and the quote should reflect that difference line by line rather than as one adjusted total.
Specification is where budgets quietly drift. Underfloor heating, triple glazing, a separate consumer unit, or a fully fitted kitchenette all add cost, and each should appear as a distinct item so you can decide whether it's worth it.
Site access matters more than most buyers expect. If a crane or a long carry is needed because the garden is landlocked, or the only route in is through a narrow side passage, that labour has to be priced.
Size, Specification and Site Access
- Footprint: A larger annex needs more materials, more insulation and more foundation work.
- Structure and finish: Timber frame, composite cladding and a pitched roof all carry different costs.
- Services: Running power, water and drainage from the house is a real cost, and it rises with distance.
- Access: Restricted gardens add labour time, which is why we ask about it before quoting.
We don't publish fixed prices, because no two gardens are the same.
Your Garden Annex Quote Checklist Before You Call
A garden annex quote checklist saves you a wasted phone call. Before you ring anyone, gather the information a surveyor will ask for anyway, and you'll get a more accurate figure and a faster turnaround.
Here's what to have ready:
- Approximate footprint you want, in metres
- Intended use: office, guest room, annexe for a relative, gym, studio
- Whether you need water, drainage or a kitchenette
- Photos of the garden from several angles
- Any known drainage, trees, or boundary disputes
- Your rough budget range
- Whether you'll be financing the build
- Your target start date
That last point about financing is worth flagging early. If you plan to spread the cost, say so at the first call, because it changes the paperwork and the timeline.
The biggest mistake we see is homeowners ringing for a figure before they've decided what the building is for. Decide the use first, then the size, then the spec. The quote follows.
Why a Garden Annex Site Survey Comes First
A garden annex site survey is a physical inspection of your plot before any figure is confirmed, and it exists because gardens lie. Ground conditions, drainage, access and boundaries all look different on a screen than they do in person.
What we look for on a survey:
- Ground conditions and whether the sub-base needs extra work
- Drainage runs and where water actually goes in winter
- Boundary lines and any shared access
- Overhead obstructions such as mature trees
- The practical route for materials and, if needed, machinery
In practice, this is the step that protects you. A quote given over the phone is an estimate, and a quote given after a site inspection is far more reliable. Every build we deliver sits behind a 10-year structural guarantee.
Garden Annex Finance Options Explained
Garden annex finance options in the UK typically fall into three buckets: savings, a secured or unsecured loan, and a regulated finance agreement arranged through the builder. Each has a different impact on your monthly outgoings and your total cost.
Savings: No interest, no paperwork, but the project waits until the pot is full.
A bank loan: Straightforward, but rates and terms vary widely, and approval depends on your circumstances.
Builder-arranged finance: Kent Bespoke Garden Rooms™ provides access to FCA-regulated finance options.
Watch out: the cheapest headline rate isn't always the cheapest deal. A longer term lowers the monthly payment but raises the total interest paid, so compare the total cost of credit, not just the monthly figure.
Ask each provider for the APR, the term, the total amount repayable and any early settlement terms. A reputable lender will hand those over without hesitation.
How to Compare Quotes for a Custom Annex
Comparing quotes for a custom annex means comparing scope, not totals. Two figures that look similar on paper can cover wildly different amounts of work, and the cheaper one often isn't.
| What to Compare | What Good Looks Like | Red Flag |
|---|---|---|
| Breakdown | Itemised by stage | One lump sum only |
| Groundworks | Priced separately | "Included" with no detail |
| Electrics | Consumer unit and runs listed | Assumed or excluded |
| Guarantee | Written, structural, dated | Verbal only |
| Payment terms | Staged, tied to milestones | Large deposit upfront |
| Survey | Done before quoting | Quote given sight unseen |
When you get a quote for custom annex work, ask three questions of every provider: what's excluded, what triggers a variation, and what happens if the ground is worse than expected. The answers separate the professionals from the salespeople.
A common mistake is choosing on price alone and discovering halfway through that drainage was never in scope. The variation charge that follows usually wipes out the saving.
Request Your Free Custom Annex Quote
The fastest route to an accurate figure is a conversation followed by a site visit, and that's exactly what we offer. You can explore our bespoke garden rooms in Kent to see the range of annexes and offices we build, then request your free quote with no obligation.
What you get from us: 25 years of construction experience, a 10-year structural guarantee on every build, and access to FCA-regulated finance if you'd rather spread the cost.
Get started with Kent Bespoke Garden Rooms™ and turn your garden into a space that earns its keep.
Frequently Asked Questions
What information do I need to get a quote for a custom annex?
Come with your intended use, rough dimensions, garden access details and any photos of the site. A garden annex quote checklist should also cover boundary positions, drainage, services such as power and water, and whether the annex needs to be self-contained with its own kitchen or bathroom. The more accurate your brief, the closer the first figure will be to the final one.
How much does a bespoke garden annex cost?
Bespoke garden annex cost varies with size, specification, site access and whether the unit is self-contained. A basic insulated studio sits at a very different point to a fully self-contained annexe with a kitchenette, shower room and separate entrance. Rather than publish a figure that will not match your brief, Kent Bespoke Garden Rooms™ quotes each build individually after reviewing your requirements and site.
Should I get a site survey before requesting a garden annex quote?
A garden annex site survey is generally a sensible step before any build, as ground conditions, drainage, access and boundary positions all affect the build method and cost.
What garden annex finance options are available?
Kent Bespoke Garden Rooms™ provides access to FCA-regulated finance options, which means the lending is arranged through a regulated provider with clear terms set out before you commit. Ask for the total repayable, the term length and any early repayment charges so you can compare the cost of borrowing against paying outright. A free quote request is the usual starting point before finance is discussed.
