Extending a Bungalow: Upwards, Outwards, or Both?
Bungalows offer a unique set of extension possibilities — including going upward to create a chalet-style home. A practical guide to bungalow extensions in Dorset.
The bungalow extension decision
Bungalows present a choice that houses do not: extend outwards (adding ground-floor space), upwards (adding a first floor), or both. Extending outwards is simpler and cheaper but eats garden space. Going upward doubles the living area without touching the footprint but is more expensive and requires planning permission in almost all cases. The right choice depends on your plot size, budget, and what you need. In Dorset, bungalows are particularly common in Broadstone, Corfe Mullen, Upton, Hamworthy, and throughout the Purbeck villages — many built in the 1950s to 1970s on generous plots that can accommodate ground-floor extensions comfortably.
Ground-floor rear and side extensions
A single-storey rear extension on a detached bungalow benefits from the same generous PD rights as a detached house — up to 8m depth under Prior Approval. A 4m x 6m rear extension (24m²) costs £40,000–£60,000 and typically creates a new kitchen-diner, freeing the original kitchen space for a bedroom, utility, or study. Side extensions are also straightforward on bungalows — many sit on wide plots with ample space on one or both sides. The main consideration is the roof: extending a bungalow's roof seamlessly requires matching the pitch, materials, and ridge height. A flat-roofed addition is cheaper but looks incongruous on a pitched-roof bungalow. Hip-to-gable at the side with a matching extension creates the best visual result.
Going upward: the loft conversion and dormer route
Many bungalows have sufficient roof height for a loft conversion, especially those with steep-pitched roofs common in the 1950s and 1960s. A rear dormer on a bungalow can create one or two bedrooms with an en-suite, turning a two-bedroom bungalow into a three or four-bedroom chalet home. Permitted Development allows up to 50m³ for detached bungalows. However, the staircase is the main challenge: it has to come from somewhere on the ground floor, typically stealing space from a hallway or bedroom. Design the staircase position before committing — a poorly placed staircase can ruin the ground-floor layout. Cost for a bungalow loft conversion with rear dormer: £50,000–£75,000 including staircase, bathroom, and finishing.
Full first-floor additions
Adding a complete first floor to a bungalow — creating a two-storey house — is a major project that requires planning permission and often a full structural appraisal of the existing foundations and walls. The existing bungalow foundations may not be deep or wide enough to support an additional storey, requiring underpinning (£15,000–£30,000). The existing walls need to be assessed for load-bearing capacity. And the neighbours will have opinions — adding a full storey to a bungalow in a street of bungalows changes the character and causes overlooking. Planning officers in Dorset are cautious about full first-floor additions in established bungalow areas. A compromise is a chalet-style half-storey with dormer windows, which is lower in profile and often more acceptable in planning terms.
Accessibility: the bungalow's superpower
Single-storey living is the bungalow's greatest asset, particularly for older residents and those with mobility issues. If you are extending a bungalow, preserve the ability to live entirely on the ground floor — even if you add bedrooms upstairs, keep a bedroom and bathroom accessible on the ground floor. Level thresholds, wide doorways, and a wet room instead of a bath make the bungalow future-proof. This is also a strong selling point: accessible bungalows in Dorset are in high demand and command a premium because the population skews older, particularly in Purbeck, Christchurch, and the coastal towns.
Written by the PlanBuildCo team
9 years designing extensions and renovations in Poole, Dorset.
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