Dormer

Dormer Loft Conversion

The most popular loft conversion type — a box-shaped extension to the roof creating a full-height room with vertical walls and windows. Compare up to 3 free quotes — no obligation.

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Dormer Loft Conversion

A dormer loft conversion adds a box-shaped structure to your existing roof slope, creating a room with full-height walls and significantly more usable floor space than a Velux conversion. Rear dormers are the most common and typically fall within Permitted Development rights — no planning permission required for most properties.

The resulting space is ideal for a master bedroom with en-suite, a home office, or a children's bedroom. Getting 3 quotes from experienced loft conversion specialists ensures you understand the true cost and what each quote includes.

What’s involved

  • Structural survey and calculation of steel beams required to support the dormer
  • Building regulations application and inspections throughout the build
  • Roof opening, installation of steel structure and dormer frame construction
  • Waterproofing and roofing of the dormer structure (flat or pitched roof)
  • First and second fix carpentry, insulation, plastering, windows and final decoration

Typical costs

Typical cost: basic rear dormer £25,000–£35,000. Dormer with en-suite £35,000–£50,000. Full-width rear dormer £40,000–£60,000.

Prices vary by region, subfloor condition and product choice. Compare 3 quotes for the most accurate price for your specific job.

FAQs — Dormer Loft Conversion

Do I need planning permission for a rear dormer?
Most rear dormer conversions on houses fall within Permitted Development rights and do not require planning permission, subject to volume and height limits. Flats, listed buildings and properties in conservation areas are excluded. Your specialist will confirm for your specific property.
How long does a dormer loft conversion take?
A typical rear dormer conversion takes 6–10 weeks from start to completion, depending on the size of the dormer, the extent of internal finishing and whether an en-suite is included.
Will a dormer conversion require building regulations approval?
Yes — all loft conversions require building regulations approval regardless of whether planning permission is needed. This covers structural integrity, fire escape, insulation and staircase design.
How much headroom do I need in the loft for a dormer conversion?
A minimum of 2.2m from floor to ridge is generally required to achieve the necessary post-conversion headroom. Your specialist will measure the loft at the survey stage.
Can any house have a dormer loft conversion?
Most houses with a pitched roof can have a dormer conversion, but the feasibility depends on roof pitch, existing structure and ceiling heights. A survey is required before quoting.
What customers say
★★★★★ 4.9 / 5 from verified customers
★★★★★

“We had a rear dormer conversion done last summer — extra bedroom and en-suite for our teenage daughter. Got three quotes through this site, saved around £4,000 compared to the first firm we spoke to. The specialist handled planning permission and building regs start to finish. Highly recommend.”

Sarah M. Surrey
★★★★★

“Hip-to-gable conversion on our 1930s semi. I was nervous about the planning application but the specialist I found here had done dozens in our street and knew exactly what to submit. Project came in on time at 10 weeks. The new master bedroom is brilliant.”

James R. Leeds
★★★★★

“L-shaped dormer on our Victorian terrace — created two rooms and a bathroom from what was a completely unusable loft. The comparison process gave me confidence I was paying a fair price. Building control sign-off came through with no issues. Absolutely transformed the house.”

Helen T. Manchester
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