A loft conversion is an excellent way to add an extra bedroom or living space to your home without extending its footprint. In 2025, the cost of a loft conversion in the UK starts at around £20,000 and can exceed £60,000.
The simplest and cheapest type is a rooflight or Velux conversion, which involves adding windows to the existing roof structure. This type of project typically costs between £20,000 and £30,000.
A dormer conversion is the most popular type, as it involves building a box-like structure out from the roof slope to create more headroom and usable floor space. A typical dormer loft conversion will cost between £35,000 and £55,000.
For those wanting to maximise space, a hip-to-gable or a mansard conversion are the most extensive options. A hip-to-gable conversion, suitable for semi-detached or end-of-terrace houses, involves replacing one of the sloping sides of the roof with a vertical wall. A mansard conversion alters the entire roof structure to create a full additional storey. These complex projects typically start from £50,000 and can go much higher.
The final cost will depend on the size of your loft, the complexity of the structural work, the quality of the internal finishes (e.g., bathroom fixtures, flooring), and your location. You will also need to factor in the cost of architectural drawings and building regulations approval.