Loft Conversions

Types of Loft Conversion

The right type of loft conversion depends on your roof structure, the headroom available and your budget. A Velux (rooflight) conversion is the simplest and most affordable option — it involves adding roof windows to the existing roof slope without altering the external shape. A rear dormer extends the roof outward to create a flat-ceilinged room with full standing height. A hip-to-gable conversion replaces the sloping side of a hipped roof with a vertical gable wall, significantly increasing usable floor area — this is particularly common on 1930s semi-detached houses. A mansard conversion replaces an entire roof slope with a near-vertical wall and flat roof above, creating maximum space but requiring planning permission in most cases.

Loft Conversion Costs

A basic Velux loft conversion typically costs between £25,000 and £35,000. A rear dormer conversion ranges from £35,000 to £55,000 depending on size and specification. Hip-to-gable conversions, which involve more extensive structural work, typically cost £45,000 to £65,000. Mansard conversions are the most expensive at £50,000 to £70,000 or more. These prices include structural steelwork, floor strengthening, staircase construction, insulation, plastering, electrics, plumbing and decoration. An en-suite bathroom adds approximately £5,000 to £10,000. The overall cost is influenced by the existing roof structure, the complexity of the staircase route, and the level of internal finish.

Planning Permission and Regulations

Most loft conversions fall under permitted development rights, meaning planning permission is not required — provided the volume added does not exceed 40 cubic metres for terraced houses or 50 cubic metres for detached and semi-detached houses, and the work does not raise the roof height above the existing ridge. However, mansard conversions, properties in conservation areas, and flats almost always require full planning permission. Regardless of planning, all loft conversions require building regulations approval covering structural safety, fire escape routes (including fire doors and smoke alarms), thermal insulation, sound insulation between floors, and staircase design. MTD Building Contractors manage the full regulatory process.

Structural Requirements

Every loft conversion requires structural engineering. The existing ceiling joists are rarely strong enough to support a habitable floor, so new steel beams and engineered floor joists are typically installed. Dormer and hip-to-gable conversions require steel supports to carry the new roof structure. The staircase opening needs trimming steels to maintain structural integrity. We coordinate all structural engineering calculations and building control inspections as part of the project.

How Long Does a Loft Conversion Take?

Most loft conversions take 6–10 weeks to complete on site. A straightforward Velux conversion is at the shorter end, while hip-to-gable and mansard conversions with en-suites take closer to 10–12 weeks. Much of the work is carried out from the outside (scaffolding and roof work) before moving inside for the fit-out, so disruption to the rest of the house is relatively limited compared to a ground-floor extension.