Loft conversion businesses adapt roof spaces into usable rooms, such as bedrooms, home offices, bathrooms or storage areas. Work commonly includes assessing the existing roof structure and headroom, installing floor supports and access stairs, and fitting insulation, lighting, ventilation and heating. The design may retain the roof shape with roof windows, or alter it with dormers or other extensions to create more floor space and headroom. Services can cover design, structural calculations, building work and interior finishing, although some firms provide only particular stages of a project. They may also advise on planning permission and building regulations, which can apply depending on the property and the proposed work. Compliance typically involves requirements for structural safety, fire protection, insulation, stairs and ventilation. Before work begins, the design and condition of the roof are assessed to establish what form of conversion is practical.