How Much Does a Garden Room Cost?

Quick Cost Breakdown

Costs vary depending on your build type and specification, but here is what a typical garden room project looks like in 2026:

• Modular or flat-pack garden room: A professionally installed modular build typically costs £8,000-£15,000 including foundations and basic electrics
• Brick-built garden room: The most durable option, typically costing £15,000-£30,000 depending on size and finish
• Garden room with shower and toilet: Adding plumbing typically adds £3,000-£8,000 to the overall build cost
• Planning permission: Most garden rooms fall under permitted development and do not require a planning application, with some exceptions.

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A Guide to Garden Room Costs

Whether you are planning a modest flat-pack build or a permanent brick structure with a bathroom, this guide covers what to expect at every budget level.

In this guide, we cover:

1. Average Garden Room Costs
2. Garden Room Cost Per m²
3. Material Options and Their Costs
4. Garden Room with Shower and Toilet Costs
5. Insulation Options for Your Garden Room
6. Additional Costs to Consider
7. How to Reduce Garden Room Costs
8. Find a Builder for Your Garden Room
9. FAQs: Common Questions about Garden Room Costs

Read on for everything you need to know about garden room costs in 2026.

Average Garden Room Costs

Garden room costs depend heavily on size, materials, and how much finishing work is included.

The table below gives a clear starting point based on common build types.

Average garden room cost by type:

Type of Garden Room	Average Cost
Self-build garden room	£1,500-£2,500
Children's playhouse	£500-£1,500
Modular or flat-pack garden room	£8,000-£15,000
Office garden room	£15,000-£25,000
Oak frame garden room	£20,000-£40,000
Brick-built garden room	£15,000-£30,000
Bespoke garden room with bathroom	£30,000-£60,000+

These figures cover the structure and basic finish. Electrics, plumbing, insulation, and interior fittings are often priced separately, so always ask your builder for a fully itemised quote before committing.

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Garden Room Cost Per m²

Comparing garden room costs by square metre is the most reliable way to benchmark quotes against each other.

Professionally built garden rooms in the UK typically cost between £1,200 and £2,500 per m², with mid-range fully finished builds sitting toward the higher end of that range once insulation, electrics, double glazing, and internal finishing are included.

The cost per m² tends to drop slightly as the build gets larger, because labour and fixed costs such as foundations and electrics are spread over a bigger footprint.

Cost by size - mid-range specification:

Size	Estimated Cost
6m² (small office)	£7,000-£9,000
12m² (medium room)	£18,000-£24,000
20m² (large room)	£40,000-£50,000

The biggest trap homeowners fall into is headline prices that exclude foundations (typically £1,500–£5,000), groundwork, VAT, and internal finishes. Always ask suppliers whether their per-m² figure is shell-only or fully inclusive - the difference can be £5,000-£15,000.

For context, a traditional single-storey house extension typically costs £2,000-£3,000 per m², making a well-built garden room a more cost-effective route to extra space in most cases. See our house extension cost guide for comparison.

Material Options and Their Costs

The material you choose for your garden room affects both the upfront cost and how much maintenance you will face over time. Each option has a different balance of cost, performance, and longevity.

• Timber frame with cladding is the most common approach for garden rooms. A timber-framed structure with timber or composite cladding offers a good balance of cost and performance. Timber cladding costs around £50-£75 per m² for materials, while composite cladding tends to run higher but requires far less upkeep over time.

• Oak frame garden rooms have strong visual appeal and good energy efficiency. Because oak is a premium material requiring careful joinery, oak frame builds typically cost £20,000-£40,000 depending on size. Build times are often faster than brickwork, as the frame arrives pre-cut from the manufacturer.

• Brick-built garden rooms are the most durable option and offer better insulation values than timber or composite alternatives. A brick build feels more like a permanent extension than a garden structure, which makes it a popular choice for spaces that will be used year-round. Brick-built garden room costs typically range from £15,000 to £30,000.

• Modular or flat-pack garden rooms use pre-built panels assembled on site. They are the fastest option to install and generally the most affordable route to a finished structure. Entry-level flat-pack kits start from around £5,000–£8,000 for materials alone, though foundations, electrics, and finishing are still required on top.

• SIPs (Structural Insulated Panels) are increasingly popular in higher-spec builds. They offer excellent thermal performance and a fast build time, with insulation built into the panel itself. SIPs panels typically cost around £100-£150 per m² for supply.

Garden Room with Shower and Toilet Costs

Adding plumbing to a garden room significantly increases both the project complexity and the overall cost. A garden room with a shower and toilet needs a connection to your existing drainage system, a cold water supply, and in most cases a hot water source. This typically adds £3,000-£8,000 to the overall build, though costs can be higher depending on how far the garden room sits from the main house.

Addition	Estimated Cost
Connecting to mains drainage	£1,500-£3,000
Shower installation	£500-£2,000
Toilet installation	£500-£1,500
Basin and pipework	£300-£800
Hot water supply (if needed)	£500-£1,500

A garden room bathroom also means the project is more likely to require building regulations approval, regardless of the overall size of the build. Factor in £200–£500 for a building regulations application if this applies to your project.

If you are planning a garden room with shower and toilet, speak to a plumber at the design stage - running pipes while the foundations and floor are being laid is far cheaper than retrofitting later. See our bathroom fitting cost guide for more on wet room and shower fitting costs.

Insulation Options for Your Garden Room

If you plan to use your garden room year-round, insulation is one area where cutting corners creates problems. Poorly insulated builds are the most common regret homeowners share when looking back on a garden room project, and retrofitting insulation after the fact is both expensive and disruptive.

• PIR rigid boards (such as Kingspan or Celotex) are the most widely used option for high-performance garden rooms. They offer an excellent thickness-to-performance ratio, which matters when wall depth is limited. PIR insulation typically costs £4-£8 per m² for materials.

• Mineral wool (glass or rock wool) is a flexible, affordable option that works well between timber studs. It is commonly used in floors and walls, though it needs to be kept dry to perform well. Mineral wool insulation costs around £3–£6 per m² for materials.

• SIPs panels have insulation built into the structure itself, which simplifies the build and delivers consistent thermal performance. This makes them a popular choice for garden offices where energy efficiency is a priority.

• Spray foam is occasionally used in retrofits but is generally not recommended for new garden room builds, due to the difficulty of future access and the concerns it raises for mortgage lenders if you ever sell your property.

For a fully insulated garden room, budget £500-£1,500 for insulation materials depending on size and specification. Labour for insulation installation is usually included in the builder's overall quote rather than priced separately. See our insulation cost guide for more on materials and fitting costs.

Additional Costs to Consider

Beyond the main structure, a number of other costs can add up quickly if you are not prepared for them. Getting a fully itemised quote that breaks these out separately is the best way to avoid surprises.

• Foundations are one of the most overlooked elements when budgeting for a garden room. A concrete slab costs around £80-£120 per m², while ground screws are faster and less disruptive at £30-£50 per m². Sloped or clay-heavy ground can push foundation costs towards £4,500 for a standard-sized build.

• Electrics are essential if you plan to use the space as an office or gym. Running a supply from your house to a small garden room costs around £800–£1,500 for a basic setup, rising to £2,000-£3,000 for a fully wired room with multiple circuits, lighting, and a consumer unit.

• Flooring adds comfort and finish to the space. Laminate flooring costs £15-£50 per m² for materials, while engineered timber runs £30–£80 per m². If you are having underfloor heating installed, factor in an additional £500-£1,500 for the system.

• Plastering a garden room costs between £1,000 and £2,000 depending on size, if you want a fully plastered interior finish rather than exposed boarding. See our plastering cost guide for more detail.

Planning permission is not usually required for garden rooms, as most fall under permitted development rules. However, if your garden room is within 2 metres of a boundary, over 2.5 metres in height, or in a listed building or conservation area, you will need to apply.

A planning application costs £258, and a lawful development certificate - useful to have even when planning permission is not required - costs £129.

How to Reduce Garden Room Costs

A garden room does not have to cost as much as the headline figures suggest. The gap between an expensive build and a sensible one is often down to a handful of decisions made early in the process, not the quality of the finished space. Start with a clear brief. The more specific you are about size, use, and materials before approaching builders, the more accurate your quotes will be. Vague briefs lead to vague quotes, which tend to expand once work begins.

Choose modular over bespoke where possible. Modular and semi-modular builds use standard components that are quicker to install, which brings labour costs down significantly compared to a fully bespoke build.

Phase the project. If budget is tight, start with the structure and insulation and hold off on electrics, flooring, and interior finishes until later. Most builders can accommodate a phased approach.

Source materials yourself. For items like flooring, lighting, and fixtures, shopping around builders' merchants and online suppliers can save a meaningful amount compared to buying through the contractor.

Use a local builder rather than a garden room company. Garden room companies charge a premium for the full-service experience. A local builder working from your specification can deliver the same result at lower cost - and you can find and compare available builders on MyBuilder by posting your job.

Find a Builder for Your Garden Room

Getting quotes from two or three local builders, rather than relying solely on specialist garden room companies, often uncovers meaningfully better value without any compromise on quality.

MyBuilder connects you with builders who have completed garden room projects near you. You can browse their profiles, read reviews from previous customers, and see photos of completed jobs before deciding who to contact.

All tradespeople on MyBuilder undergo checks at registration, such as ID documents, company details, certifications for regulated jobs and skill assessments, allowing you to hire with confidence.

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FAQs: Common Questions about Garden Room Costs

Do I Need Planning Permission for a Garden Room?

Most garden rooms do not require planning permission, as they fall under permitted development rules for outbuildings. The key conditions are that the structure is single-storey, the eaves height does not exceed 2.5 metres, and the garden room does not cover more than 50% of your garden area.

If your property is listed, in a conservation area, or the structure will sit within 2 metres of a boundary at a height above 2.5 metres, you will need to apply. Always check with your local planning authority if you are unsure.

How Long Does It Take to Build a Garden Room?

Build time varies by construction method and complexity.

Modular and flat-pack garden rooms can be assembled in as little as one to three days once the base is in place. Timber frame builds typically take one to two weeks. Brick-built garden rooms and bespoke structures can take two to five weeks or longer. Groundworks, electrics, and any building regulations inspections all add time to the overall timeline.

Can I Use a Garden Room as a Home Office All Year Round?

A well-insulated garden room with heating and electrics works well as a year-round home office. The key is proper insulation, PIR boards or SIPs panels with a U-value below 0.18 W/m²K will keep the space warm in winter without running up significant energy bills. A basic plug-in panel heater is often sufficient for a small office; a larger space benefits from underfloor heating or a small electric radiator on a thermostat.

You can browse photos of completed garden office projects on MyBuilder to get a sense of what is achievable at different budgets and see the standard of work from local builders.

Is a Brick Garden Room Worth the Extra Cost?

Brick garden rooms cost more to build and take longer than timber or modular alternatives, but they offer superior insulation, durability, and longevity. If you are planning to use the space heavily year-round, a brick build can make financial sense over a 10 to 20 year horizon compared to a timber structure that may need re-cladding or significant maintenance. Brick also tends to add more to property value than a modular unit, particularly if the room is built to a high standard.

How Much Does It Cost to Add Electrics to a Garden Room?

Running electrics to a garden room from your main house typically costs £800-£1,500 for a basic setup, rising to £2,000-£3,000 for a fully wired room with a dedicated consumer unit, multiple circuits, external lighting, and data cabling. The exact cost depends on the distance from the house, the number of circuits required, and whether any groundwork is needed to bury the cable.

All electrical work must be signed off under Part P of the Building Regulations.