UK's Most Popular Loft Conversion

Dormer Loft Conversion Specialists

A dormer loft conversion costs between £25,000 and £45,000 in the UK, making it the most popular type for terraced and semi-detached homes.

A dormer loft conversion adds a flat-roofed box to your roof slope, which sharply increases headroom and usable floor space. We handle the planning and building regulations from start to finish. You'll get a free estimate up front, then a fixed-price quote once we've surveyed your loft.

From £25,000

Timescale: 8–12 weeks

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What is a Dormer Loft Conversion?

A dormer loft conversion is a box-shaped extension built out from the slope of your existing roof. It swaps angled rafters for vertical walls and a flat roof, which turns awkward attic space into a proper room. That is why it is the UK's most popular loft conversion type. It suits almost every house style and delivers the biggest gain in usable floor area and standing headroom.

A Velux conversion simply adds roof windows to the existing slope, so the loft keeps its original sloping shape. A dormer, by contrast, physically extends the roof outward. As a result, the new room can span the full width of your house or just part of it. Expect vertical walls, a flat or low-pitch roof, and large windows that flood the space with daylight.

The good news is that most rear dormers qualify as Permitted Development, so you won't need planning permission. However, a front dormer or one in a conservation area usually needs a full planning application. Either way, we handle the whole permission process for you, from the first checks through to approval.

Key Benefits of a Dormer Conversion

Maximum Headroom

Vertical walls replace sloped rafters, giving you full standing height across the entire floor area.

Maximum Floor Space

The box extension adds significant square footage — often 20–30 m² of usable room.

Versatile Configuration

Use the space as a bedroom, home office, playroom, or master suite with en-suite bathroom.

Strong PD Success Rate

Most rear dormers pass under Permitted Development — no planning fees, no delays.

Is a Dormer Conversion Right for My Home?

A dormer loft conversion suits most UK homes, from terraced houses to detached properties. In practice, the one firm requirement is a roof ridge at least 2.2 m above the loft floor. That single measurement decides whether the room will have proper standing height. Use this quick checklist to see how your property measures up:

Semi-detached or detached house — most straightforward PD case for a rear dormer
Terraced house — rear dormer permitted subject to volume limits (40 m³)
Roof ridge height of at least 2.2 m above the loft floor (we check on survey)
Pitched roof of any angle — dormers work on both shallow and steep pitches
Property NOT in a conservation area or Article 4 direction zone (PD still possible with care)
Property NOT a listed building (listed building consent required — we advise)

Not sure where your home stands? Book a free survey and we'll measure the head height, check the roof structure, and confirm suitability. It costs nothing and carries no obligation.

A beautifully finished loft bedroom created from a dormer conversion — A dormer conversion creates a proper full-height bedroom — not just a boarded loft.

What's Included in Every Dormer Conversion

Every dormer conversion we deliver is a complete, end-to-end package. In other words, one agreed price covers the design, the permissions, the structural work, and the build itself. You won't get separate bills from architects, engineers, or trades. Here's exactly what you get:

Free site survey and feasibility assessment

Architectural drawings and design

Permitted Development check or full planning application

Building regulations submission and approval

Structural engineer calculations and specifications

All scaffold, plant, and materials

Dormer frame, flat roof, and weatherproofing

New dormer windows (uPVC or timber, your choice)

Insulation to building regs standard (warm roof)

Stud walls, plasterboard, and first-fix electrics

New staircase and fire-rated landing door

Final clean, snagging, and building regs sign-off

Typical Cost and Timescale

A dormer loft conversion typically costs from £25,000 and takes 8–12 weeks on site. Your exact price depends on the size and specification of the dormer. For example, a full-width box with an en-suite costs more than a single-room dormer. That's why every project starts with a free estimate, followed by a no-obligation survey.

Cost Guide

From £25,000

Full project cost including all planning, structural, and build work. Final price depends on property size, dormer dimensions, specification, and location.

Build Programme

8–12 weeks

From commencement on site to building regs sign-off. We complete the planning and structural design before the build starts, so nothing holds the team up once they arrive.

Every quote we give after the survey is fixed-price, with no hidden extras. Once you've signed the contract, we never ask for more money unless you change the agreed scope of work. Until then, your estimate and survey cost nothing and carry no obligation.

Frequently Asked Questions

How big can a dormer conversion be under Permitted Development?

Under Permitted Development rights in England, a rear dormer can extend to within 20cm of the roof ridge. Volume limits apply too. The dormer must not add more than 40 cubic metres on a terraced house, or 50 cubic metres on a detached or semi-detached one. In addition, it must not be visible from the front, and it must use materials similar to the existing house. We carry out a full PD check as part of every free survey.

Will a dormer loft conversion need building regulations approval?

Yes. Every loft conversion needs building regulations approval, even when you don't need planning permission. Building regs cover structural strength, fire safety, insulation, staircase design, ventilation, and electrical work. We submit the application on your behalf. At completion, a building inspector signs off the work and you receive a completion certificate.

Can I add an en-suite bathroom to a dormer loft conversion?

Absolutely. A dormer conversion is the most popular choice for adding a master bedroom with en-suite. The box dormer creates ample headroom and floor space for a shower, toilet, and basin. Better still, we handle all the plumbing and drainage routing as part of the project. See our en-suite loft conversion page for more detail.

How disruptive is a dormer loft conversion to live through?

Most of our customers carry on living at home throughout the build. The main structural and roofing work happens in the first two to three weeks. After that, your home is weathertight and the remaining work moves indoors. We use protective sheeting and clean up at the end of every working day. On top of that, our project manager walks you through what to expect, week by week, before work starts.

Does a dormer loft conversion add value to my property?

Yes. A dormer loft conversion consistently delivers one of the strongest returns of any home improvement. According to Nationwide Building Society data, adding a bedroom via a loft conversion can increase property value by up to 20%. In most UK markets, the added value exceeds the cost of the conversion itself. As a result, a dormer is both a lifestyle upgrade and a sound financial investment.

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