Garden Room vs. Home Extension: A Cost Breakdown

The Real Cost of “Just Adding More Space”

If you’ve looked at moving house or building an extension recently, you’ll already know the feeling.

Shock.

Then disbelief.

Then a quiet “how is this even possible?”

In 2026, the cost of space has exploded. Stamp duty. Legal fees. Builder delays. Labour shortages. Material inflation. Suddenly, adding a bit of breathing room to your home feels financially reckless rather than sensible.

financially reckless rather than sensible.

And yet, the problem hasn’t gone away.

You still need space.

Privacy.

A place to think.

That’s why so many homeowners are now asking a very specific question:

Is a garden room actually better value than a home extension?

Let’s break it down.

The True Cost of a Traditional Extension

A standard brick-built extension in the UK now typically costs:

• £2,000–£3,000 per m²
• A 20m² extension = £40,000–£60,000
• That’s before overruns, design changes, or ground issues

Add to that:

• Months of disruption
• Builders walking through your house daily
• Dust. Noise. Stress.
• Planning delays and neighbour objections

Extensions can add value to a property.

But they come at a high emotional and financial cost.

The Garden Room Alternative

Now compare that with a high-spec, insulated garden room.

• Typical installed cost: £12,000–£20,000
• Cost per m²: often under £1,000
• Installed in days, not months, typically one day for a 12m2 garden room
• No disruption inside the house

You still get:

• A permanent, usable room
• Year-round comfort with proper insulation
• A dedicated space that feels separate

For many households, this is the first time the numbers actually make sense.

Planning Permission: Simpler Than You Think

One of the biggest myths is that planning permission is required.

Many garden rooms fall under permitted development if:

• They’re single-storey, so under the height limits
• Used as ancillary space (office, studio, gym)
• Kept 1m away from the boundary
• etc

That removes costs, delays, and risks.

For anyone looking for small garden solutions, this is a massive win.

Does a Garden Room Add Value?

Short answer: yes.

Longer answer: it depends on how it’s built.

A properly installed, insulated garden building can:

• Increase buyer appeal
• Improve home functionality
• Support hybrid work lives
• Add usable square footage without altering the main house

Estate agents increasingly highlight garden offices as selling points, especially soundproof garden office setups for remote workers.

 The Smarter Financial Decision

Here’s the honest truth.

If you need:

• A bigger kitchen
• A structural change
• More bedrooms inside the house

An extension may still be right.

But if you need:

• Your own space
• A place to work, think, train, or unwind
• A faster, cleaner solution

A garden room wins on cost, speed, and sanity.

In 2026, that matters more than ever.