Bungalows are highly sought-after properties, but their single-floor layouts can sometimes feel cramped. Fortunately, bungalows occupy larger plots than typical modern houses, making them ideal candidates for expanding outwards (single-storey extensions) or upwards (loft extensions and roof lifts).
In this 2026 cost guide, we look at average bungalow extension costs per square metre, conversion prices, architectural fees, and how to find vetted builders on GetBuilder.
Average bungalow extension costs by type in 2026
The construction path you choose determines your total build costs. Extending outwards is typically cheaper per square metre but eats up garden space. Extending upwards requires complex roof alterations but preserves your outdoor land:
- Single-Storey Extension (Outwards): Typically costs £1,900 to £3,500 per m² (averaging around £2,750 per m²). A standard 30 m² rear extension costs £57,000 to £105,000.
- Dormer Loft Conversion: Typically costs £40,000 to £75,000 (averaging £50,850). Adds a bedroom and head height to the existing loft.
- Complete Loft Extension (Upwards): Typically costs £70,000 to £140,000 (averaging £105,000). Often involves reinforcing the foundation and building a brand-new second floor.
- Roof Extension (Roof Lift): Typically costs £27,000 to £45,000 (averaging £35,000). Ideal if you only need to raise the roofline slightly to create structural clearance.
Bungalow extension cost comparison by size
For a standard single-storey brick extension building onto the back or side of a bungalow, expect the following average total budgets:
| Extension Size | Budget Specification | Premium Specification |
|---|---|---|
| Small (15 m²) | £28,500 | £52,500 |
| Medium (30 m²) | £57,000 | £105,000 |
| Large (50 m²) | £95,000 | £175,000 |
Professional drawings and architectural fees
A bungalow extension requires planning drawings and building regulations calculations before construction begins:
- Planning Drawings: £950 - £2,500 for basic floorplans and elevation blueprints.
- Architect Fees: Expect 8% to 12% of the overall build cost for a full design and project management service.
- Structural Engineer: £600 - £1,500 to design joist support calculations and check foundation loading limits.
Key cost factors for bungalow extensions
- Foundation reinforcements: Bungalows were originally designed to support only a single floor. If you choose to extend upwards (adding a second storey), your structural engineer may require you to underpin the existing foundations, adding £5,000 to £15,000 to your builder's quote.
- Groundworks and utilities: Moving external drains, gas feeds, or electrical junction boxes to make way for a ground floor extension can add £2,000 to £5,000 to the cost.
- Glazing options: Fitting standard double-glazed windows is cost-effective, but adding large bi-fold doors, sliding glass walls, or structural roof lanterns can add £3,000 to £10,000 to the bill.
How to hire a builder on GetBuilder
To ensure your structural extension is built safely and within building regulations, follow these steps:
- Obtain proper planning drawings: Never ask a builder to quote without completed architectural drawings.
- Verify insurance: Ensure your general builder has valid public liability and structural warranty insurance.
- Use GetBuilder: Post your project plans for free on GetBuilder. We'll connect you with vetted local builders who can provide detailed quotes. Compare reviews, check ratings, and hire securely.
