Types of Loft Conversion Explained

Not all loft conversions are the same — and the type that is right for your Maidenhead property depends on your roof structure, your budget, the floor area you want to create, and in some cases the planning constraints on your specific address. The most common mistake homeowners make is choosing a conversion type based on what they have seen on another property without checking whether it is achievable or appropriate for their own.

This post explains the main loft conversion types available in Maidenhead, what each involves, which property types they suit, what they cost in the current Maidenhead market, and what the planning position looks like for each.

Rooflight Conversion

What It Is

A rooflight conversion — sometimes called a Velux conversion — retains the existing roof pitch entirely. No dormer, no external alteration to the roofline. New rooflight windows are added for light and ventilation, a new structural floor is installed, insulation is fitted between and over the rafters, a new staircase provides access, and the space is finished internally to create a usable room.

Which Properties It Suits

A rooflight conversion only works where the existing ridge height gives sufficient standing room once insulation is accounted for — typically where the ridge is at least 2.4 metres above the existing ceiling joists. Many of Maidenhead’s inter-war semis in Furze Platt and Cox Green have enough pitch to achieve this. Post-war properties — Boyn Hill, Braywick, Woodlands Park — are more variable, and some are simply too low to create a usable room without raising the roofline.

Planning

In most circumstances, a rooflight conversion is permitted development — no planning application needed. It is the conversion type most clearly within PD in almost every case, including many conservation area properties where a dormer would require a planning application.

Cost

Rooflight conversions are the most cost-effective conversion type. For a standard Maidenhead property: £22,000–£35,000.

Trade-offs

Less natural light than a dormer. Smaller usable floor area — the roof pitch limits where you can stand comfortably. For a simple additional bedroom where budget is the priority and the headroom is adequate, it is a well-proven and sensible option. For a primary bedroom suite where floor area, natural light and specification matter, a dormer almost always delivers a better result.

Dormer Loft Conversion

What It Is

A dormer conversion extends out from the rear roof slope, creating a vertical rear wall with full-height windows. The result is a substantially larger and better-lit room than a rooflight conversion — a proper double bedroom with an en-suite of reasonable size. The structural work involves a new floor frame tied into the existing structure, the dormer frame, cheek walls, a flat roof over the dormer, and weatherproofing at the junction with the existing roof. Once the dormer is weathertight, internal fit-out proceeds: insulation, boarding, first fix plumbing for the en-suite, internal walls, second fix, tiling, sanitaryware and decoration.

Which Properties It Suits

The dormer is the right conversion type for the majority of Maidenhead properties. The inter-war and post-war semis of Furze Platt, Cox Green and Boyn Hill convert well with a full-width rear dormer. Victorian and Edwardian terraces in the town centre suit a rear dormer. The larger detached properties across the Thames villages can accommodate large, high-specification dormers as part of a wider loft suite.

Planning

Most rear dormers on semi-detached and detached Maidenhead properties fall within permitted development. Conditions: additional volume must not exceed 50 cubic metres for semis and detached (40 for terraced), the dormer must not project beyond the plane of the existing roof at the front, and must not exceed the ridge height. In conservation areas — Cookham, Bray — dormers may require a full planning application and the design needs to meet Royal Borough character requirements.

Cost

For a standard rear dormer on a Maidenhead semi: £36,000–£58,000. For a larger dormer or higher specification, up to £70,000+ on the larger detached properties.

Hip-to-Gable Conversion

What It Is

On end-of-terrace and detached properties with a hipped roof — where the end of the roof slopes inward to a point — the hip end limits the usable loft floor area. A hip-to-gable conversion removes the sloping hip and replaces it with a new vertical gable wall. Hip-to-gable is almost always combined with a rear dormer to maximise floor area from both directions.

Which Properties It Suits

End-of-terrace and detached properties. In Maidenhead, this conversion is most common on the larger detached properties of Cookham, Bray and Taplow, and on end-of-terrace properties in the town centre and the older residential streets. It is also carried out on suitable detached properties across Furze Platt and Cox Green.

Planning

Hip-to-gable conversions almost always require a planning application. The Royal Borough of Windsor and Maidenhead determination period runs eight to ten weeks from a valid submission. In conservation areas, the application needs to address character and materials requirements.

Cost

For a standard hip-to-gable with rear dormer on a Maidenhead property: £48,000–£78,000. For a higher-specification conversion on a larger Thames-side property: £80,000–£110,000+.

Mansard Conversion

What It Is

A mansard rebuilds the rear roof slope at a near-vertical angle — typically 70 degrees or more — and installs a flat roof at the top. The result is a near-full-height rear wall that maximises both the floor area and the ceiling height. The style is common in London period terraces and is most appropriate on larger Victorian and Edwardian properties in Maidenhead where maximum floor area is the priority.

Which Properties It Suits

Larger Victorian and Edwardian properties — particularly terraces and semis in the town centre and the older residential streets of Maidenhead. Less common in Maidenhead than in inner London but carried out on suitable properties.

Planning

Mansard conversions almost always require a planning application. The complete rebuilding of the rear roof slope is well outside permitted development in virtually every case. In conservation areas, the Royal Borough will scrutinise materials and design carefully.

Cost

For a standard mansard conversion on a Maidenhead property: £62,000–£95,000+.

Which Type Is Right for Your Maidenhead Property?

The right conversion type depends on four things: your roof structure, your budget, the floor area and specification you want to achieve, and your planning position.

A rooflight conversion is right where the headroom is sufficient, the budget is the priority, and permitted development is a firm requirement. A dormer is right for most Maidenhead semis and terraces where creating a proper bedroom and en-suite is the goal. A hip-to-gable is right where the property has a hipped end and maximum floor area is the brief. A mansard is right where the property is Victorian or Edwardian and maximum ceiling height throughout the conversion is needed.

The best way to establish which type suits your property is to have a builder assess the roof structure and talk through the options with you before any design is committed to. Get in touch and we will come out to take a look.