Dormer Loft Conversions in Derby

Types of dormer

• Full-width rear dormers

  Run almost the full width of the rear roof. The most space for the money, and common on terraces and semis.

• Set-in rear dormers

  Sit within the roof, with tiles left showing on either side. A little less space, with a lighter look that suits many detached houses.

• L-shaped dormers

  On houses with a back outrigger, dormers over the main roof and the outrigger roof join up, often making room for two bedrooms or a bedroom and bathroom.

• Hip-to-gable with a dormer

  On a semi or detached house with a hipped roof, the side is built up into a gable and a rear dormer added, getting the most out of the loft.

  All loft conversion types

• Small pitched dormers

  Individual dormers with their own small pitched roof, used where a large box dormer wouldn’t suit the house.

• Bungalow dormers

  Dormers on a bungalow roof turn the loft into a first floor of bedrooms and a shower room.

Cost and timescale

• £55,000–£85,000 Typical dormer loft conversion
• £60,000–£70,000 Where most projects fall
• +£8,000–£15,000 To add an en-suite
• 6–8 weeks On site, or 8–10 for L-shaped dormers

1. Weeks 1–2 Scaffolding goes up at the back, the tiles come off where the dormer will be, and new floor joists go in.
2. Weeks 3–4 The dormer frame, walls, flat roof and windows are built and made weathertight.
3. Weeks 5–6 Wiring, any bathroom pipework, insulation and the new staircase.
4. Weeks 7–8 Plastering, sockets and lights, flooring, skirting and bathroom fittings, then the final inspection.

Wider dormers, steelwork for long spans, asbestos or a difficult site push the cost up, and you’ll get an itemised quote once we’ve surveyed the roof. Finance can spread the cost, subject to status.

Dormers and planning permission

A rear dormer on a house is usually permitted development when it meets these conditions:

Condition	What it means for the dormer
Position	On the rear or side slope, never the front slope facing a road
Volume	Up to 40 m³ added on a terrace, or 50 m³ on a semi or detached house, including any earlier roof additions
Height	No higher than the existing ridge
Eaves	Set back about 20 cm from the eaves where practicable
Finish	Materials similar in appearance to the existing house
Side windows	Obscure-glazed and non-opening below 1.7 m

Dormers aren’t permitted development on flats or in conservation areas and National Parks, and a front dormer always needs an application. On a terrace or semi, the dormer’s steels usually bear on the party wall, so the Party Wall etc. Act 1996 applies, with notice to the neighbours at least two months before that work starts. Building regulations approval covers the structure, the fire escape route, the stairs and the insulation.

Planning the room

Put the bed against the full-height dormer wall, wardrobes along the side walls, and drawers or low storage under the front slope where the ceiling drops. In a bathroom, the shower goes under the flat dormer ceiling where the headroom is greatest. Our joiners build eaves cupboards and wardrobes to fit the slopes, so none of the floor is wasted.

Dormer loft conversion questions

How much does a dormer loft conversion cost?

Typically £55,000 to £85,000, with most projects between £60,000 and £70,000. That covers the dormer itself, the floor, insulation, windows, staircase, electrics, plastering and building regulations fees. An en-suite adds about £8,000 to £15,000, and L-shaped dormers cost more than a standard rear dormer.

Do I need planning permission for a rear dormer?

Usually not on a house, provided the dormer stays within the permitted development volume, sits below the ridge and is set back from the eaves. Flats, listed buildings, conservation areas and front dormers need an application, as do houses whose rights have been removed.

How long does a dormer loft conversion take?

Usually 6 to 8 weeks on site. L-shaped dormers and conversions with an en-suite can take 8 to 10 weeks. You'll have a written programme before work starts.

Can you fit an en-suite in a dormer?

Yes, and the extra headroom is one of the main reasons people choose a dormer. A full shower, toilet and basin fit comfortably, with the shower under the flat dormer ceiling where the height is greatest.

Should I choose a dormer or a Velux conversion?

If your loft already has good height and you mainly want one room, a Velux conversion costs less and is quicker. If the loft is low, or you want a double bedroom with an en-suite and space to stand up across the floor, a dormer is usually worth the extra.