Garage Conversion Planning and Cost Guide for London Homeowners
A garage conversion is one of the most cost-effective ways to add habitable space in London without reducing the garden. Where a garage is attached to or integrated within the main dwelling, conversion typically adds a usable room at lower cost than a ground-up extension of the same floor area — because the shell already exists.
Do You Need Planning Permission for a Garage Conversion?
In most cases, converting an existing integral or attached garage to habitable use falls within Permitted Development — meaning no formal planning permission is required. The conversion is an internal change of use rather than an external addition.
However, PD rights don't apply if: the property is in a conservation area or subject to an Article 4 direction that removes PD rights; the garage is a detached structure not connected to the main dwelling (where PD rights for change of use may be different); the conversion involves external alterations that materially affect the appearance of the building; or the planning permission for the original house included a condition requiring the garage to be retained for vehicle parking.
If your property was built with parking conditions attached to its planning consent — common in areas where councils were managing parking supply — check the original planning permission before starting a garage conversion. Breaching a parking condition can result in enforcement action.
Building Regulations for Garage Conversions
Garage conversions always require Building Regulations approval. The main areas covered include: structural adequacy of the existing floor and walls for habitable use; thermal performance — the existing garage walls and roof are typically well below habitable insulation standards and will need significant upgrading; fire safety, including fire-resisting doors between the garage and the rest of the house; ventilation, particularly if the new room has limited natural light; and drainage, if a toilet or bathroom is being added.
The floor of a garage is typically at a lower level than the main house floor, with a step down. This creates both a practical challenge (how to create a level transition) and a structural one (the floor may need to be raised with new insulation and screed). On some properties, the garage floor is below the main house damp-proof course level, which creates additional waterproofing considerations.
What Does a Garage Conversion Cost in London?
Basic conversion (insulation, plastering, electrics, floor finish, internal door upgrade): £15,000–£25,000 for a standard single garage.
Conversion with new window or door opening: add £2,000–£5,000 for the structural work and new units, depending on specification.
Conversion with en-suite or utility addition: add £8,000–£15,000 depending on the extent of plumbing and bathroom specification.
High-specification conversion (bespoke fit-out, bi-fold to garden, etc.): £35,000–£60,000+.
These figures assume London labour rates. VAT at 20% is additional on all figures for VAT-registered contractors.
rcbGroup handles garage conversions as standalone projects and as part of wider house refurbishment packages across London.