A garage conversion is one of the best-value home improvement projects you can do in London. You are adding habitable floor space to your home without extending the footprint — the structure is already there, you are simply changing how it is used.
How much does a garage conversion cost in London?
The typical range for a garage conversion in London is:
£15,000 – £30,000 for a standard single integral or attached garage converted to a usable room (home office, bedroom, playroom, or utility room).
The range is wide because cost depends heavily on what the room will be used for, whether a toilet or shower is being added, the condition of the existing structure, and the level of finish.
What drives the cost?
Garage type
There are three main types of garage in London:
Integral garage — built into the ground floor of the house, with the house structure above. The most common type in post-war semis and terraces. These are straightforward to convert as no new foundations or external walls are needed.
Attached garage — a separate structure sharing one wall with the house. Slightly more involved as the roof and remaining walls must be checked, and the connection to the house may require a new opening.
Detached garage — completely separate from the house. Most complex and expensive to convert to habitable use, as insulation, drainage, and utility connections all require more work. Often requires planning permission.
What the room will be used for
A home office or playroom is simpler and cheaper than a bedroom with an en-suite bathroom. Adding a toilet or shower room adds £4,000–£8,000 to the project cost, depending on drainage complexity.
Insulation and thermal performance
All garage conversions require Building Regulations sign-off, which includes meeting current thermal performance standards. Insulating the floor, walls, and ceiling to Part L standards is non-negotiable. This is included in a properly scoped conversion — do not accept a quote that doesn't explicitly cover it.
Structural condition
If the existing garage structure has movement, damp penetration, or a roof nearing the end of its life, remedial work may be needed before the conversion can proceed. A site survey will identify this before pricing is finalised.
Typical cost breakdown
For a standard integral single-garage conversion to a home office or bedroom (no bathroom):
- Structural check and enabling works: £500–£1,500
- Floor insulation and new screed or board: £1,500–£2,500
- Wall insulation and plasterboard: £1,500–£2,500
- Ceiling insulation and plasterboard: £800–£1,500
- New garage door replacement (window or door): £1,500–£3,500
- Electrical first fix and second fix: £1,500–£2,500
- Plastering: £800–£1,500
- Decoration: £600–£1,200
- Building Regulations fees: £400–£700
Total: approximately £9,000–£17,000 for a basic conversion without bathroom.
Adding a shower room or WC typically adds £4,000–£8,000, bringing the total to £13,000–£25,000 or more depending on specification.
Do you need planning permission?
In most cases, converting an integral or attached garage does not require planning permission. It is considered a change of use within the existing dwelling footprint and falls under permitted development.
Planning permission may be required if:
- Your property is in a conservation area and the conversion changes the external appearance
- You are converting a detached garage
- Your property's original permitted development rights have been removed (check your title deeds or call the local authority)
- You are in an area with Article 4 Directions restricting change of use
We check the planning position before every project.
Do you need Building Regulations approval?
Yes, always. A garage conversion is a material change of use — the converted room must meet the same Building Regulations standards as the rest of your house. This covers structural stability, insulation, ventilation, fire safety, electrical work, and drainage if a bathroom is included.
Building Control will inspect the work at key stages and issue a completion certificate on sign-off. This certificate is important — mortgage lenders and buyers' solicitors will ask for it if you sell the property.
We manage the Building Regulations process as part of every conversion we carry out.
How long does a garage conversion take?
A standard single garage conversion typically takes 4–6 weeks on site. A conversion with a bathroom addition or more complex structural work may take 6–8 weeks. We provide a programme before starting.
Is a garage conversion worth it in London?
In most parts of London, yes — adding a usable room at £15,000–£25,000 adds more value than it costs in most property types, particularly in areas where space comes at a premium. A converted garage also avoids the planning risk and cost of a full extension.
The key is doing it properly — with full Building Regulations compliance and a completion certificate. An unconverted or poorly converted garage that lacks sign-off can complicate a sale and may need to be reversed.
See how RCB handles garage conversions →
For a free site survey and fixed-price quote, call or WhatsApp us on 07359 872594.