How to compare garden room quotes A checklist, and the questions to ask

Before contacting anyone, write a short brief: the footprint, what the room is for, where it will sit in the garden, roughly what glazing is wanted, and whether it needs heating, data or a shower room. Send the same brief to each company.

Three quotes is the usual number. Fewer leaves little to compare against, and more than four or five tends to add confusion rather than information. Prices for similar rooms vary by up to 100% between companies, so a single quote says little about the market.

A firm quote should follow a site survey. The survey is where the surveyor checks the ground, the levels, the route for the power cable and how materials will reach the garden, and those decide several of the costs below. A price given before anyone has seen the site is an estimate. The price calculator gives a fair starting figure for any size before the first call.

One company prices a room ready to use, with the base, the connection to the house and a heater. Another prices the building and leaves the rest to the buyer. Both are honest prices for different things.

Download it as a PDF to print, or copy it into a spreadsheet, and fill in one column per company. Where a quote doesn’t mention an item, mark it as a question to ask rather than assuming it is included.

Take each quote and add VAT if it is missing, then an allowance for anything that isn’t included: about £1,000–£6,500 for foundations depending on size and type, £1,500–£3,500 for the power connection, and each firm’s own figures for delivery, heating or data. Two quotes that looked £5,000 apart can end up close together, or further apart.

Once the prices are like for like, set them against the market. In our October 2026 survey of 42 UK companies’ published prices, a typical 3m × 3m garden room costs about £19,700 and a 5m × 3m about £25,500, including VAT and installation. Most buyers spend £15,000–£35,000 on a well-insulated room for year-round use. Small rooms cost more per square metre, because the doors, windows and electrics cost much the same at any size.

A quote well below the others is worth a second look rather than a quick yes. The difference usually turns out to be scope, a thinner structure or less insulation, a cheaper roof covering, or a shell that leaves the interior to the buyer. A quote well above the others may simply include more, or may reflect a brand rather than the building; the specification is how to tell.

Once the room is finished most of it can’t be seen, which is why it needs to be in writing.

Structure. Most garden rooms are built from Structural Insulated Panels (SIPs) or an insulated timber frame, and both come in different weights. A timber frame might use 47mm × 150mm studs, or 47mm × 100mm at closer centres; both are sound, while 47mm × 70mm is noticeably lighter. SIPs range from about 75mm to 175mm thick. A heavier structure costs more and gives a stiffer building with more room for insulation.

Insulation. Compare U-values, not thickness. A U-value is the rate at which the roof, walls or floor lose heat, and a lower number is better. Thickness alone says little: 50mm of rigid PIR board can outperform 150mm of fibreglass. If a specification gives only millimetres, ask for the U-values instead.

Cladding. Ask what the cladding is, how it has been treated and how often it needs attention. Cement fibreboard and good composites need the least upkeep. Cedar and larch can be left to weather to silver-grey. Treated softwood needs re-treating every three to five years, and a painted finish needs repainting. Some companies will mix two claddings, putting the costlier board on the side facing the house to keep the price down.

Doors and windows. Aluminium frames are generally a higher specification than uPVC. Count the opening sections as well as the glass: full-height fixed glazing brings in the light, but the room still needs windows that open for air.

Roof covering. EPDM rubber membranes and insulated steel panels are the common choices and are designed to last decades. A few companies still fit roofing felt as standard, with EPDM as an upgrade. Felt has a shorter life and more seams, where leaks start; EPDM is usually laid in a single sheet.

Interior. An unfinished interior leaves the decorating to the buyer. Wall panelling is quick and easy to keep clean, though the joints show. Plastered and decorated walls feel like a room in the house, cost more and add time on site.

Electrics and heating. Check the number and position of sockets against how the room will be used, and whether an outside socket or a data point is included. Some companies leave heating out on the basis that the room is well insulated; a small heater is still worth having in the coldest weeks.

Ask for the schedule in writing, and compare how much is paid before anything arrives on site. A balance held back until the room is finished and signed off gives the buyer some leverage if anything needs putting right.

Ask how the deposit is protected. Many established companies offer deposit insurance, which covers the money if they stop trading before the room is delivered. On a larger project the deposit can exceed the cover limit, so check the figure. If the room needs planning permission, ask whether the deposit is refundable if the application is refused.

Paying part of the price by credit card brings Section 75 of the Consumer Credit Act into play, which makes the card provider jointly liable if things go wrong. It applies where the cash price is over £100 and no more than £30,000, so it may not cover a larger room. Check the terms with the card provider.

Most companies guarantee their buildings for five to 10 years, usually covering the structure, the roof covering, and the doors and windows. Read what is excluded, such as cracks in plaster or doors that drop, and how quickly problems have to be reported and fixed. A standard guarantee depends on the firm still trading. An insurance-backed guarantee pays for repairs if it closes, which makes it worth asking for.

The checklist settles what can be measured. Some of the choice can’t be, so score each company out of 10 on the points that matter most: how well they listened at the design stage, whether the design answers the brief, the specification, the scope of the price, the guarantee and the timescale. Add the scores alongside the adjusted prices.

The cheapest quote is not always the best value, and the most expensive is not always the best building. Some higher-priced rooms turn out less well specified than cheaper ones once the details are side by side. The firm that was easiest to deal with during the design is also the one the buyer will deal with for the length of the guarantee.