Dreaming of more space without turning your home into a building site or blowing your savings? Short answer: yes, garden rooms are usually cheaper than extensions. They're quicker, easier, and often don’t need planning permission.
But is it the right move for your home? Let’s break it down and find out what fits your budget, and your lifestyle.
If you’re torn between building an extension or adding a garden room, here’s the truth:
Garden rooms usually cost less, take less time, and involve far less hassle. Whether you're building a backyard office or a stylish retreat, the difference in cost and disruption is often night and day.
Let’s get into the numbers.
For a basic setup, a garden room typically costs between £1,500 and £2,500 per square metre. That includes standard insulation, electrical installation, and a simple interior finish.
Go premium, think smart heating, bi-fold doors, luxury finishes, and costs can rise to £2,500–£3,000 per m².
Still, it's a bargain compared to the cost of building onto your house.
A single-storey extension can set you back anywhere between £1,800 and £3,000 per m². And that’s before you get into the extras like structural adjustments or custom design features.
Extensions also require deeper groundwork and full integration with your home, which increases both labour and material costs.
Let’s say you want 20m² of extra space:
Garden Room: £30,000–£50,000
Extension: £40,000–£60,000
Double-storey Extension: £60,000–£100,000+
Even with top-tier features, a garden room comes out cheaper. It’s also done faster and usually with fewer unexpected bills.
At first glance, it might seem like bricks and mortar should offer more value, but the reality is more complicated.
Here’s why building an extension can hit your wallet hard.
Extensions need to match the foundations of your existing home. That means deep digging, drainage work, and reinforced footings.
It’s essential for structural safety but comes at a price. In contrast, garden rooms often use simple concrete pads or screw piles, keeping costs and labour light.
Building an extension? Expect a long list of expensive materials, bricks, blocks, plaster, roofing tiles, and more.
Garden rooms, on the other hand, often use prefabricated timber frames or SIPs. These materials are quicker to install and usually cheaper, without compromising on insulation or comfort.
You’ll need professionals for an extension: architects, structural engineers, and maybe even a planning consultant.
These fees often add 5–10% to the total cost, even before construction starts. Garden rooms, especially modular ones, usually come with design included or require far less professional input.
Extensions involve altering your existing layout, knocking through walls, moving electrics or plumbing, and sometimes reconfiguring your whole ground floor.
Each change opens the door to unexpected costs, like hidden pipework or dodgy wiring. A detached garden room? No knock-throughs, no headaches.
Beyond the price tag, extensions often come with a side of stress. Let’s look at the stuff that rarely makes it onto quotes, but definitely affects your life.
Most garden rooms fall under permitted development, meaning you often don’t need formal planning approval.
Extensions? Not so lucky. They usually require full planning permission, including applications, drawings, waiting times, and potential revisions.
With a traditional extension, you’re automatically under the watchful eye of building control. That means site visits, inspections, certificates, and, sometimes, costly upgrades if things aren’t up to code.
Garden rooms might not require full building regs, depending on size and usage. That’s one less hoop to jump through.
A modern garden room can be installed and ready to use in just 2–4 weeks.
An extension? 3–6 months of dust, drills, and detours through your back door. If you’re working from home or have small kids, that’s a serious lifestyle disruption.
Ever lived through a home reno? It’s noisy, messy, and stressful.
With an extension, builders are inside and around your main living areas, sometimes cutting off your kitchen or bathroom. Garden rooms are built in the garden, away from your day-to-day life.
As brilliant as garden rooms are, they’re not perfect for every situation. There are times when a full extension really is the better fit.
Dreaming of an open-plan kitchen-diner? You’ll need an extension.
Garden rooms are usually stand-alone structures, which makes them less suited to connected living areas.
Want your house to go from a 3-bed to a 4-bed on Rightmove?
Only a proper extension can add an official bedroom to your property listing. A detached garden room doesn’t count, even if it’s insulated and furnished beautifully.
While garden rooms can boost property appeal and add up to 5–10% value, a well-designed extension usually delivers more in the long run.
Extra bedrooms, bathrooms, or open-plan living areas tend to add bigger resale value than stand-alone spaces.
| Feature | Garden Room | Traditional Extension |
|---|---|---|
| Cost | £1,500–£3,000 per m² | £1,800–£3,000 per m² |
| Speed | 2–4 weeks | 3–6 months |
| Planning & Regulations | Often not required | Always required |
| Disruption | Minimal | Major |
| Use & Integration | Great for offices, studios, gyms | Best for kitchens, bedrooms, living |
So, is a garden room cheaper than an extension? Yes, and not just in cost. You’ll save time, stress, and paperwork too.
If you're looking to add a home office, hobby space, gym, or peaceful retreat, garden rooms are an excellent solution. They're stylish, quick to install, and won’t turn your house into a construction zone.
But if your needs are more long-term or you want to transform the heart of your home, a traditional extension might be worth the investment, just be ready for the extra time and cost.
In the end, it’s not just about saving money. It’s about choosing the right kind of space to improve how you live, work, and relax.
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