What is a Dormer Loft Conversion?

A dormer is a structural extension that projects vertically from the plane of a sloping roof. It creates additional headroom and floor space in the loft area, making it more comfortable and functional.

Types of Dormer Conversions

• Flat Roof Dormer – Most common, offers the most space.
• Shed Dormer – Sloped roof in the same direction as the main roof.
• Gable Fronted (Doghouse) Dormer – Pitched roof, traditional look.
• Hip Roof Dormer – Slopes on three sides, more complex and expensive.
• L-Shaped Dormer – Ideal for mid-terrace houses; combines two dormers.

Pros

• Increases internal space significantly
• Adds natural light via windows
• Improves property value
• Usually falls under Permitted Development (but check local rules)

Cons

• Aesthetic impact (some find it bulky)
• Flat roofs can require more maintenance>
• Cost varies depending on size and complexity

Estimated Cost (UK 2025)

Basic dormer: £30,000–£50,000

Larger or L-shaped dormers: £45,000–£70,000+

Planning Permission

Often not required if it falls under Permitted Development.

You will need planning permission if:

• It extends beyond the existing roof plane facing a road.
• It exceeds the height of the existing roof.
• You’re in a conservation area.

Building Regulations

Regardless of planning permission, building regs approval is required, covering:

• Structural integrity
• Fire safety
• Insulation
• Staircase access