Rooflight, dormer or hip-to-gable: choosing a loft conversion type

Rooflight (Velux) conversions

A rooflight conversion leaves the roof profile alone and adds windows set into the slope. The floor is strengthened, insulation is added between and under the rafters, a staircase goes in and the space is plastered out.

It suits lofts that already have generous height at the centre. Because the outline of the house does not change, it is the least disruptive type and the one most likely to fall within permitted development. The trade-off is floor area: usable standing space is limited to the middle of the room.

• Needs good existing height at the ridge
• Least change to the look of the house
• Standing room limited to the centre
• Usually the quickest of the three to build

Dormer conversions

A dormer projects out from the roof slope with vertical walls and a flat or pitched top. A full-width rear dormer is the most common version because it turns a sloping ceiling into near full-height space across most of the room — enough for a bedroom with an en-suite.

Dormers are the type most people picture when they think of a loft conversion. Rear dormers often fall within permitted development on houses; front dormers and those on properties in conservation areas usually need planning permission. The external finish — tile-hung, slate-effect, render or timber — is part of the design conversation.

Hip-to-gable conversions

Many semi-detached and end-of-terrace houses have a hipped roof, where the end slopes back towards the ridge. That slope eats into loft space. A hip-to-gable conversion builds the end wall up vertically and extends the ridge across, creating a much larger loft.

It is often paired with a rear dormer to maximise space. It is more involved structurally than a rooflight conversion and changes the side view of the house, so matching materials matters.

What decides between them

Roof shape and existing head height come first. Next is what you want the room to do — a home office can live happily under a rooflight, while a bedroom with a shower usually needs a dormer. Then there are staircase position, planning constraints and how the addition will look from the street.

Staircase and head height rules are covered in more detail in our separate guide, because they often decide what is achievable in a smaller loft.

• Existing ridge height and roof pitch
• Hipped or gable-ended roof
• Intended use: office, bedroom, en-suite
• Where a staircase can land without losing a bedroom
• Conservation area or listed status

What every type shares

All three need building regulations approval covering structure, fire escape, insulation and stairs. All involve strengthening the floor, often with new joists, and all need careful weatherproofing while the roof is open. We plan the programme so the roof is opened and closed as quickly as possible.

Anthony runs loft conversions with our own team, covering the structural carpentry, stairs, insulation and plastering.

What is a mansard loft conversion?

A mansard conversion substantially reshapes the roof, typically creating a steep lower roof slope beneath a much shallower upper section. Windows are often set into the steep face. This form can provide more usable headroom than the original sloping roof, but it involves a different scale of alteration from inserting rooflights or adding a dormer.

Feasibility depends on the existing structure, neighbouring rooflines and planning context. A mansard will usually need planning permission, and structural design, stairs, fire safety and insulation still need resolving. Understanding the type helps compare design options; whether it is suitable for your home needs a property-specific assessment.

Common questions