Garden Room vs Extension: Which Is Better Value?
Garden rooms cost less and build faster than extensions. But they are detached from the house, unheated by default, and add less resale value. This guide compares both options honestly.
The details
Cost comparison
A quality insulated garden room (15m²): £15,000–£30,000. A rear extension (15m²): £40,000–£60,000. The garden room is roughly half the cost. But the extension becomes part of your home — heated, connected, and counted in the property's square footage.
Year-round usability
Modern insulated garden rooms are usable year-round with electric heating. However, they are separate from the house — you need to walk outside to reach them. Extensions integrate directly into your home's floorplan, with access from existing rooms. For daily use (kitchen-diner, living room), extensions win. For dedicated use (office, gym, studio), garden rooms are excellent.
Resale value
Extensions are counted in your property's measured floor area and add 5–15% to value. Garden rooms are valued as outbuildings — they add appeal but not measured floor area. Estate agents value a 15m² extension far more than a 15m² garden room.
| Factor | Garden Room | Extension |
|---|---|---|
| Cost | £15,000–£30,000 | £40,000–£60,000 |
| Build time | 1–3 weeks | 10–16 weeks |
| Planning | Usually PD | Usually PD |
| Building Regs? | Usually exempt | Yes |
| Resale value added | Marginal (outbuilding) | 5–15% (floor area) |
| Year-round comfort | Good (with insulation) | Excellent (part of house) |
| Disruption during build | None (external) | High (kitchen affected) |
| Best for | Office, gym, studio | Kitchen, living room, bedroom |
Our verdict
Choose a garden room if you need a dedicated workspace, gym, or studio at a lower cost. Choose an extension if you want to expand your core living space (kitchen, living room) — the extra cost delivers significantly more resale value and daily convenience.
Common questions
Frequently asked questions
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