Conversion types

Types of loft conversion explained

Each conversion type suits different roof shapes, budgets and space requirements. Here is how they compare.

Dormer loft conversion

A dormer extends vertically from the existing roof slope, creating additional floor space and headroom. It is one of the most common loft conversion types in the UK.

Key advantages

✓Adds usable floor area and full standing headroom
✓Works with most standard roof shapes
✓Often falls within permitted development at the rear

Typically suits: Terraced, semi-detached and many detached homes.
Relative cost: Moderate
Planning: Rear dormers are frequently permitted development; front dormers usually are not.

Hip-to-gable conversion

A hip-to-gable conversion extends the sloping side of a roof into a vertical gable wall, squaring off the loft and adding significant internal volume.

Key advantages

✓Creates a much wider, more usable loft
✓Can be combined with a rear dormer for maximum space
✓Blends well with the existing roofline

Typically suits: Detached, semi-detached and end-of-terrace properties with a hipped roof.
Relative cost: Moderate to high
Planning: Often permitted development, but check volume allowances and any local restrictions.

Mansard loft conversion

A mansard changes the roof structure to create a nearly vertical rear wall and a flatter roof, providing the largest increase in usable space of any conversion type.

Key advantages

✓Maximum floor area and headroom
✓Suits period terraced properties architecturally
✓Can accommodate several rooms

Typically suits: Terraced and end-of-terrace period homes, especially in towns and cities.
Relative cost: High
Planning: Usually requires planning permission because the roof shape changes substantially.

Velux or rooflight conversion

A rooflight conversion keeps the existing roof shape and adds roof windows, with structural strengthening, insulation and a staircase inside the current loft space.

Key advantages

✓The most cost-effective option
✓Quickest to build with least disruption
✓Rarely needs planning permission

Typically suits: Lofts that already have sufficient head height, typically 2.2m or more.
Relative cost: Lower
Planning: Normally permitted development as the roof profile is unchanged.

L-shaped dormer

An L-shaped dormer joins a dormer over the main roof with a second dormer over a rear outrigger or back addition, forming an L in plan.

Key advantages

✓Delivers two rooms plus a bathroom in many homes
✓Makes use of otherwise wasted outrigger roof space
✓Excellent value per square metre added

Typically suits: Victorian and Edwardian terraced homes with a rear back addition.
Relative cost: High
Planning: Often permitted development at the rear, subject to volume limits.

Modular loft conversion

A modular conversion is manufactured off site and craned into position, with the existing roof removed and the prefabricated loft fitted in its place.

Key advantages

✓Very fast installation on site
✓Factory-controlled build quality
✓Less prolonged disruption at home

Typically suits: Properties with good crane access and a straightforward roof structure.
Relative cost: Moderate to high
Planning: Depends on the resulting roof shape; a dormer-style module may need permission.

Not sure which suits your home? Start a free quotation and select “Not sure” — a specialist will advise at your free survey.

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