What does a garden room really cost, and why do quotes vary so much?

Typical UK price ranges

These are broad market ranges for a supplied and fitted insulated garden room in the South East, including a suitable base and power, at the time of writing. They are a sanity check for budgeting, not a quote, because ground conditions and access change the groundworks element significantly.

Indicative UK garden room ranges by size and specification. Footprint | Simple insulated spec | Higher specification. Around 3m x 2.5m — £12,000 to £18,000 — £18,000 to £25,000; Around 4m x 3m — £18,000 to £26,000 — £26,000 to £38,000; Around 5m x 4m — £26,000 to £38,000 — £38,000 to £55,000; Room plus shower and WC — Add £6,000 to £12,000 — Depends on drainage runs Ranges are general UK market figures for budgeting only. Your written quote after a site visit is the real number.

The five things that move the price most

If you want to understand a quote quickly, look at these before you look at the cladding.

Groundworks: sloping plots, poor access and clay soil all add labour and material before anything is built · Insulation depth and continuity: a genuinely warm building costs more in materials and detailing than a lightly insulated one · Glazing: large aluminium sliders are a big line item next to a standard door and window set · Internal finish: taped and jointed boards cost less than a plastered and decorated interior · Services: distance from the consumer unit, trench length, and whether you want water and waste

Where people accidentally spend more later

The cheapest quote often becomes the most expensive building. Retro fitting insulation, replacing a base that has settled, or bringing uncertified electrics up to standard costs more than doing it once.

The other common one is heating. A thin building needs a bigger heater, which then runs for longer, every winter, forever. Insulation is a one off cost. Heat loss is a subscription.

How to compare two quotes fairly

Put them side by side and check they describe the same building. If a line is missing from one quote, it is not free, it is just not there yet.

Base type, thickness and whether spoil removal is included · Insulation type and thickness in floor, walls and roof · Roof covering, falls and how rainwater leaves the building · Electrical work, certification and whether the trench is included · Internal finish level: boarded, skimmed, or skimmed and decorated · Waste removal, and reinstatement of any lawn or path used for access

Getting a real figure

We are based in Tunbridge Wells and quote garden rooms across Kent, Sussex and Surrey after visiting the site, because the ground and the access genuinely change the number. The quote is written, itemised and free.

Frequently asked questions

Why is one garden room quote thousands cheaper than another?

Usually the base, the insulation depth or the internal finish. Compare the written specification line by line rather than the headline figure, and check whether groundworks and certified electrics are included.

Is a garden room cheaper than an extension?

Per square metre it usually is, because there is no structural connection to the house, no party wall issues and generally no building control application for a plain room. It is a different kind of space though, not a like for like swap.

Do I pay VAT on a garden room?

Work on an existing home is normally standard rated, so quotes from VAT registered contractors will include VAT. Ask whether a figure is inclusive so you are comparing like with like.

Can I spread the cost by finishing the inside myself?

You can, and some people do. Keep the structure, insulation, roof and electrics with the builder, because those are the parts that are expensive to correct later.

Does the price include getting rid of the spoil?

It should be stated either way. Digging a base produces a surprising amount of material, and removal has a real cost that some quotes leave out.