How much does a garden room cost?

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Price guide

£3,400 - £76,000







Low, median and high bar chart distribuiton

One practical way to have an extra room in your area is to build an outdoor space. An outdoor room can also be a garden, visitors' area, home office, man cave, or home gym. 

The cost of a garden room extension is £850 to £3,800 per square metre. Therefore, the lowest cost of building a studio in a garden with a two-by-two-floor measurement is £3,400.

The average cost of the extension is £2,000 per square metre. So if you want to know how much you will be spending on a three-by-three-metre house extension, it will probably cost you around £18,000. We know how troublesome it is to build a room extension. Garden extension is faster than a direct house extension, as nothing needs dismantling or alteration.a well-ventilated garden room

Garden room extension costs

Outdoor rooms are rising in popularity as home improvement products. They increase the size of a property’s living space, thereby adding value to your place. The house extension cost will depend on the size of your area.

Sample Room Size

Average Cost

2m x 2m (4 sqm)

£3,400 to £15,200

2m x 4m (6 sqm)

£5,100 to £22,800

3m x 3m (9 sqm)

£7,650 to £34,200

3m x 5m (15 sqm)

£12,750 to £57,000

4m x 4m (16 sqm)

£13,600 to £60,800

4m x 5m (20 sqm)

£17,000 to £76,000

The cheapest you can find for a four-square-metre room is £3,400, while a 20-square-metre room can cost you as much as £76,000. To prepare your budget, multiply the two sides of the area to get the square metre. And then multiply them by the price provided.

Factors affecting house extension prices 


You can choose between modular and bespoke designs. A modular garden room is pre-made and ready for installation, while a bespoke one is tailor-made for your wants and needs. Prices differ for basic flats, modern design rooms, patios, and oakwood garden rooms.


The base of a garden room must be in top condition to withstand sudden weather changes. We suggest asking a professional to assess your area, as they know the best base to use. 

A concrete slab base involves deep excavation and a mixture of concrete, bricks, and stone). Plinths are suitable for smaller garden rooms. Professionals use reinforced concrete as the base of a room, protecting it from pressure.

Another option is ground screws. Instead of digging a hole, professionals drive large screws of 1.2 m to 5.0 m into the ground to provide a base to build your frame. Bases usually start at £1500.


Some people choose to have a garden room without electricity. However, if you decide to host a small party in the area, you might need more than an extension cord. The cost of installing a power system for your garden room depends on your local electricianFor installation, expect to add £1,000 to £2,000 to your budget.

a fully furnished garden room


Most garden rooms require the same building techniques as typical room extensions in your house. Therefore, insulated roofs, walls, and floors are vital to your garden room construction. You can opt for timber cladding or an oakwood outdoor room for no-fuss insulation. 

Otherwise, consider using structural insulated panels or SIPs, which have a foam core in between two structures for more protection inside your room. Prices start at £600 to £1000


Working with an interior designer can cost more. However, having an extra comfortable room will add value to your home. Door and window installation starts at £600.

Kitchens and Bathrooms

Having a kitchen and bathroom installed in your garden room extension is wise. However, it can cost around £500. Prices depend on the materials you choose.


The delivery of materials depends on your location. While most companies offer free delivery, it is best to discuss it with tradespeople for accurate quotes.


A builder’s labour cost for outdoor rooms is usually £150 per day. It's better to talk to your contractor so that you can agree on a specific number of days to finish the project. This can help you set a budget for your garden room extension.

Planning permissions or building permits for garden rooms

Most garden extensions don't require planning and building permits, as long as you comply with the following conditions:

  • The room isn't in front of the house.
  • The room shouldn't occupy more than 50% of your land area.
  • The room should have a single storey, with eaves not more than 2.5 metres high. The height of the garden room should be less than 3 metres high, and 4 metres is allowed for a dual-pitched roof. However, if the room is within two metres of your boundary, the maximum height is 2.5 metres.
  • Balconies, verandas, or raised platforms aren't allowed.
  • The room shouldn't be a residential place. If you want it to have a kitchen or bathroom, you should visit your local authorities’ planning department. A planning application will cost you more or less £170.

Planning permissions are essential if you live in a conservation area (a national park or world heritage site).

Building permits

A building permit is essential, especially if you need certificates when you decide to sell your house. You will need a building permit if:

  • Your area is 15 to 30 square metres, and you intend for it to be an extra room for accommodation.
  • The room is more than one metre from your boundary and made of non-combustible materials.
  • The room needs to install electric or plumbing systems.

Visit your local authorities or the building regulations approval website for more specific details.

Finding a Tasker to work on your garden room

Looking for a skilled tradesperson to do the job can be a headache, especially when there are several things to work on. It is vital to find professional architects, roof installers, and plumbers

You can visit the Home Owners Alliance in the UK to check if they're part of associations like the National Federation of Builders or NICEIC for electricians. Subsequently, you can ask for the Tasker's portfolio to check their previous projects.

Taskers can help you complete your outdoor/garden room project. Here are the things you need to list so that we can’t find the right match for you:

  1. The service you need
  2. Measurement of the area
  3. Your budget
  4. Your location
  5. Extra jobs you require (e.g., electrical or plumbing installation)

Take the stress away and let Airtasker do the job for you!

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A garden room usually takes one to four weeks to finish, depending on the size of your area and if it's modular or bespoke.
Help your builder/tradesman by removing rocks, trees, shrubs, and other obstructions. Remember that an even area results in a faster building process.

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