Guide

Types of loft conversion explained

Choosing the right conversion type is the single biggest decision in a loft project. Here is how the main options compare in space gained, cost and planning.

Rooflight or Velux conversion

The simplest and cheapest option. The existing roof shape is untouched and windows are fitted into the slope. It only works where there is already sufficient head height, typically 2.4 metres or more at the ridge.

Dormer conversion

A dormer projects vertically from the roof slope, creating full standing headroom and usable floor area. Rear dormers are the most common conversion in UK terraced and semi-detached homes and frequently fall within permitted development.

L-shaped dormer

Two dormers joined at right angles, usually over the main roof and a rear outrigger. Common on Victorian and Edwardian terraces, and capable of creating a large bedroom plus an en-suite.

Hip-to-gable conversion

The sloping hip end of the roof is built up into a vertical gable wall, squaring off the loft. It suits detached, semi-detached and end-of-terrace homes and is often combined with a rear dormer.

Mansard conversion

The most extensive option: the rear roof is rebuilt at a near-vertical angle with a shallow flat roof above. It delivers the greatest space, costs the most, and usually requires planning permission.

Modular loft conversion

The structure is built off site and craned into place, which shortens the time your home is open to the weather. Costs are comparable to a dormer, but access for a crane is essential.

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