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Lofts and upward extensions

Dormer loft conversions

Box or full-width dormers that turn a sloping loft into full rooms. Designed, approved and built by SK Residential, with a fixed price in writing for the agreed specification.

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What is a dormer loft conversion?

A dormer loft conversion builds a box-shaped extension out from the rear slope of the roof, creating vertical walls and full head height across most of the new floor. It is the most popular type of loft conversion because it gives the most usable space for the cost.

Full-width rear dormer loft conversion clad in grey tiles on a red-brick terraced house

Rear dormers on terraced and semi-detached houses are often permitted development in England. We size the dormer to fit the volume allowance, clad it to suit the house (tile-hanging, render, slate or zinc) and fit out the room and en-suite below.

Typical time on site
8 to 12 weeks
Guide price
£50,000 to £90,000
Building regulations
Required

What is included?

  • Volume calculation and permitted development check
  • Lawful development certificate or planning drawings
  • Steelwork and new floor structure
  • Dormer frame, roof covering and cladding
  • Staircase, insulation and plasterboard
  • En-suite, electrics and fire-protected escape route

How much does a dormer loft conversion cost?

A full-width rear dormer with a bedroom and en-suite typically costs around £60,000 to £80,000 including VAT.

Dormer loft conversionsGuide price incl. VAT
Rear dormer, bedroom only£50,000 to £65,000
Full-width dormer with en-suite£60,000 to £80,000
L-shaped dormer (over rear outrigger)£65,000 to £90,000

Unit: per conversion. Guide ranges only; your price is fixed in writing after the survey.

Use the guide price tool for a figure based on your size and specification, or see all guide prices.

Does a dormer loft conversion need planning permission?

England

In England many loft conversions are permitted development: the extra roof volume must stay within 40 m³ on a terraced house or 50 m³ on a semi or detached house, nothing can sit higher than the existing ridge, no dormer can face a road on the main elevation, and side windows must be obscure-glazed and non-opening below 1.7 m. Houses in conservation areas, National Parks and National Landscapes cannot use these roof-extension rights, so dormers there need planning permission (a rooflight-only conversion can still be permitted development), and flats always need permission. A lawful development certificate is worth having as proof.

Wales

Wales has its own loft and roof permitted development rules. Rear dormers within set volume limits are often allowed, but the detail differs from England's, so we confirm the current Welsh limits against your roof before the design is fixed.

Scotland

In Scotland, dormers and other roof enlargements usually need planning permission, especially on the front of the house. A building warrant is needed before work starts in every case.

Northern Ireland

In Northern Ireland, roof enlargements such as dormers often need planning permission depending on size and position. Building control approval is needed for every loft conversion.

What about building regulations?

Full building regulations approval: structure, staircase, fire safety, insulation and ventilation.

What should I think about before starting?

  • Dormers on the front of the house facing a road are not permitted development in England.
  • Dormer cheeks close to a shared wall can trigger the Party Wall Act.
  • A flat dormer roof needs proper falls and a quality membrane.
  • L-shaped dormers are common on Victorian terraces with a rear outrigger.

How does the project run?

  1. Tell us about the project. Call, use the guide price tool or send the form with a few photos and a postcode.
  2. Free site visit. We measure up, look at access, drains and the structure, and talk through options and budget.
  3. Design and fixed price. You get drawings and a written price for the agreed specification before anything is ordered.
  4. Build and hand over. Our teams build to the programme, building control inspects, and you get the completion paperwork at the end.

Questions about dormer loft conversions

How much does a dormer loft conversion cost?

Typically £50,000 to £80,000 including VAT, and up to around £90,000 for an L-shaped dormer.

Is a dormer permitted development?

Rear dormers in England often are, within the 40 m³ (terrace) or 50 m³ (semi or detached) volume allowance. Front dormers facing a road are not.

How long does a dormer conversion take?

Around 8 to 12 weeks on site.

What cladding can a dormer have?

Tile-hanging to match the roof, render, slate, timber or zinc, depending on the house and any planning conditions.

Can a dormer include a bathroom?

Yes. The full head height in a dormer makes it the best place for a shower room or en-suite.

Related projects

Guides

Where do we build dormer loft conversions?

We take on dormer loft conversions across England, Wales, mainland Scotland and Northern Ireland. Choose your area:

Planning an extension, loft or new home?

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