What Are Prefab Garden Rooms? 

The UK garden room market was worth £266 million in 2024 and is forecast to keep growing at 5.8% a year through 2030. That growth isn’t a coincidence. More people than ever need extra space at home, but buying a larger property isn’t realistic for most families. A traditional extension takes months, costs a fortune, and turns your home into a building site.

Prefab garden rooms solve all three problems at once. They give you a brand new, fully usable room without the chaos.

In this guide, you’ll learn exactly what a prefabricated garden room is, how it compares to a traditional extension, what it costs, whether you need planning permission, and what you can use it for. By the end, you’ll have everything you need to decide if one is right for your home

That single distinction matters more than it might seem.

Traditional buildings are constructed piece by piece in your garden, exposed to weather delays, labour shortages, and the unpredictability of any outdoor build. A prefab garden room is built in controlled conditions, quality-checked before it leaves the factory, and installed in a matter of hours. Hully Pods, for example, are placed in less than a day.

The term “prefab” covers a range of build types. Some arrive as flat-pack kits you assemble yourself. Others, like Hully Pods, come fully built and are craned into position. The key features they all share: off-site manufacture, fast installation, and a ready-to-use finished space.

Materials vary by manufacturer. Common choices include timber frames, SIP panels (Structural Insulated Panels), and composite cladding. Hully Pods use a design inspired by boat hull construction and have a fibreglass outer shell, which gives them an unusually strong and weather-tight structure for their price point.

Prefab garden room vs. traditional extension: what’s the difference?

A prefab garden room is faster, cheaper, and far less disruptive than a traditional home extension, while still giving you a permanent, functional extra room. The two main trade-offs are that a garden room is detached from the house and sits in your garden rather than extending the existing floor plan.

Here’s how the two options compare directly:

The cost difference is partly about materials, but also about labour. As this breakdown of prefab vs. traditional builds explains, traditional extensions spend most of the budget on on-site labour. With a prefab, most work happens in the factory, which dramatically reduces what you pay per square metre.

A prefab garden room also doesn’t require you to knock through walls, redirect plumbing, or rewire your home. Those “hidden” costs are exactly what pushes traditional extension budgets so far over the original quote.

Do prefab garden rooms need planning permission?

In most cases, no. Prefab garden rooms in the UK fall under Permitted Development rights (Class E), which means you can build without a formal planning application, provided your structure meets a few straightforward conditions.

The main rules to know:

• The garden room must not cover more than 50% of the total garden area (including any existing outbuildings)
• It must not be positioned in front of the main wall of your house
• If it’s within 2 metres of a boundary, it cannot exceed 2.5 metres in height
• It cannot be used as a separate self-contained living space or sleeping accommodation

For a full breakdown of the rules and any local exceptions, read our garden room planning permission guide.

There are a few situations where you will need planning permission regardless. These include listed buildings, conservation areas, National Parks, and properties that are flats or maisonettes, which don’t have Permitted Development rights. If you’re in any doubt, check with your local planning authority before you order.

One useful step even when planning permission isn’t required: apply for a Lawful Development Certificate. It costs around £206 in application fees (2025) and gives you formal proof of compliance, which solicitors may ask for when you sell your home.

What can you use a prefab garden room for?

This is where prefab garden rooms really stand out. Because they’re fully insulated, weatherproof, and can be wired for electricity, they function as proper rooms rather than glorified sheds.

The most popular uses:

Home office. The most common reason people buy a garden room. A dedicated workspace just steps from your back door removes the distractions of working from home without a commute. For practical setup tips, see our guide on how to extend WiFi to your garden office.

Garden gym. A private gym you can use at any time, with no membership fees. Our garden gym pods are built to handle the weight and use of regular training sessions.

Beauty salon or dog grooming. A fully separate space to run a small business from home, with its own entrance and a professional feel.

Gaming or entertainment room. A dedicated space for screens, consoles, and speakers without taking over a room in the house.

Guest room. With the right insulation and heating, a garden room makes a comfortable place for guests to stay. Note that using it as permanent sleeping accommodation may affect your planning permission status, so check first.

Classroom or tutoring space. Schools, nurseries, and private tutors have all used garden rooms to create extra learning environments.

The current average costs per square metre break down roughly like this:

• Prefabricated kit: £800–£1,400/m²
• Professional build: £1,800–£2,800/m²

What drives the price up: size, wall thickness and insulation level, glazing choices (bifold doors, skylights), electrical installation, and cladding materials. What keeps it down: standardised designs, off-site manufacture, and minimal on-site labour.

Don’t forget to factor in what base your pod will need. A concrete base typically runs around £190 per cubic metre, and this cost is separate from the pod itself in most cases.

One thing worth noting: a well-insulated room costs more upfront but saves money long term. A poorly insulated structure will be expensive to heat in winter and unusable in summer. For guidance, see our tips on how to keep your garden room warm in winter.

Insulation

A proper garden room should be comfortable all year round, not just in summer. Look for insulated walls, floors, and roofs with suitable U-values for the UK climate. Thin, uninsulated panels are usually a sign of a seasonal product rather than a true garden room.

Cladding and weatherproofing

High-quality composite or treated timber cladding lasts significantly longer than untreated wood and requires far less maintenance. EPDM rubber roofing has become the modern standard for flat-roof garden rooms because of its durability and watertight performance.

Structure and engineering

This is where Hully Pods stand apart from much of the market. Rather than relying on a conventional timber-box design, the Pods take inspiration from marine engineering. Their curved fibreglass shell is designed to deflect wind and rain naturally, improving structural strength and weather resistance.

The outer shell is built from robust, durable fibreglass, the same material trusted in boats built to withstand harsh British coastal conditions. If it is strong enough for the sea, it is more than capable of handling year-round British weather in gardens across the UK. The shell is engineered for longevity and is designed to last for decades, with a projected lifespan of 20 years or more.

Estate agents increasingly view well-built garden rooms as genuine value-adding features, particularly when they are fully insulated and finished to a high standard. A quality garden room is not just useful today,  it is an investment in your property for the future.

Conclusion

Prefab garden rooms are one of the most practical ways to add space to your home in the UK right now. They’re fast to install, far cheaper than a traditional extension, and don’t require planning permission in most cases. Whether you need a home office, a gym, a guest room, or a professional workspace, a good prefab garden room will serve you for years.

Hully Pods are designed to make this as straightforward as possible. Prices start from £2,995 including VAT and delivery, and installation takes a few hours. 

Ready to find the right size for your garden? Compare all Hully Pod sizes and configurations and find the one that fits your space and budget.

Frequently Asked Questions