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Across Hampshire

Rear dormer design and planning guide

The most popular loft conversion type across Hampshire — and the one we design most often. A rear dormer creates a full-height room in your loft with minimal disruption and, in most cases, no planning permission required.

Planning your project? Try our loft conversion cost calculator for an indicative cost and planning view for your address.

Hampshire Build prepares planning and building regulation drawings for Building Notice submission. Required structural calculations are prepared by an independent qualified structural engineer.

What Hampshire Build Provides

  • Measured site survey of your existing roof and loft space
  • Planning drawings — floor plans, elevations, sections
  • Permitted Development assessment and LDC application where needed
  • Building regulation drawings prepared for Building Notice submission, with structural calculations by an independent qualified structural engineer
  • Structural engineer coordination (Premium Package)
  • Fixed-fee from £1,950+VAT — no hourly billing

What Is a Dormer Loft Conversion?

A dormer loft conversion extends vertically from the existing roof slope to create a box-shaped structure with a flat or pitched roof. Unlike a Velux conversion — which simply installs windows into the existing slope — a dormer breaks out of the roofline to create additional head height and floor space that would otherwise be unusable due to the sloping ceiling. See our dormer loft conversion Hampshire service.

The vast majority of dormer conversions in Hampshire are rear dormers — positioned on the rear slope of the roof, away from the street. This is both the most structurally straightforward approach and, in most cases, the one that falls within Permitted Development rights, allowing the work to proceed without a formal planning application.

A well-designed rear dormer on a typical Hampshire three-bedroom semi-detached house can create a full double bedroom with en-suite bathroom — taking a property from three to four bedrooms and adding significant value. For detached properties, the dormer can span the full width of the rear slope, creating an even larger room.

Hampshire Build designs dormers across Winchester, Basingstoke, Southampton, Andover, Fareham, Eastleigh, and the surrounding areas. Our drawings are prepared to building control standard — ready for your chosen builder to price and construct without ambiguity.

Planning Permission for Dormer Conversions

Permitted Development (No Application)

  • Rear dormers up to 40m³ on semi-detached houses
  • Rear dormers up to 50m³ on detached houses
  • Dormer must not exceed existing ridge height
  • Materials similar in appearance to existing house
  • No side-facing windows at first floor level or above
  • Property not in a conservation area or Article 4 area

Planning Permission Required When...

  • → The property is in a designated conservation area
  • → An Article 4 Direction removes PD rights
  • → The property is a listed building
  • → The dormer exceeds the Permitted Development size limits
  • → Side dormers facing a road are proposed
  • → Previous extensions have used the PD allowance

Hampshire Build checks your property's exact planning status and advises on the correct route before any design work begins.

Fixed-Fee Pre-Build Packages

All prices exclusive of VAT. No hourly rates.

Pre-Build Package

£1,950 + VAT

Professional on-site measured survey; planning drawings and application; building regulation drawings; independent qualified structural engineer calculations.

Most Popular

Premium Package

£2,950 + VAT

Everything in Pre-Build Package, plus: detailed schedule of works; contractor vetting and two proposals; client-focused building contract.

Most Complete

Premium Plus Package

£3,950 + VAT

Everything in Premium Package, plus: staged programme of works mapped to contractor payments; Building Notice submission; one Party Wall notice to one adjoining owner.

Dormer Loft Conversion Design — Areas We Cover

Winchester Basingstoke Southampton Andover Fareham Eastleigh

Frequently Asked Questions

A rear dormer may qualify for permitted development if all relevant conditions are met. The additional roof-space volume limit is 40m³ for terraced houses and 50m³ for other houses; previous roof additions count towards that allowance. Roof height, position, materials and the property's planning history also matter. Conservation areas, Article 4 Directions and listed buildings require property-specific checks with the local planning authority.
Our package fees are Pre-Build £1,950 + VAT, Premium £2,950 + VAT and Premium Plus £3,950 + VAT. Compare the packages page for the agreed scope. Structural calculations are prepared by an independent qualified structural engineer.
Building regulation drawings are prepared for Building Notice submission. Where the project requires structural calculations, these are prepared by an independent qualified structural engineer. Project-specific drawings may cover insulation, fire escape, drainage and stair design. Building regulations approval is required for loft conversions regardless of whether planning permission is needed.
Your measured survey is booked within 10 working days of your deposit. Your first drawings follow within 15 working days of the survey. Hampshire Build prepares the planning drawings and submits the planning application where required. Building regulation drawings are prepared for Building Notice submission.

Book Your Complimentary Consultation

Discuss your dormer conversion with Hampshire Build. We will assess your property, confirm the design options available, and provide a fixed-fee price. No obligation.

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