Getting started

Garage conversions are fast gaining popularity — why? Because so many of us are realising that we rarely use our garage space for storing our cars and they can add more value as habitable rooms. A garage conversion could, therefore, be one of the most cost effective and simplest ways to extend your home, without actually increasing its footprint.

Do I need planning permission?

Planning permission for a garage conversion is not necessary in many cases, although it is always best to double check with your local authority first.

Most integral garage conversions fall under Permitted Development which means there is no need to make a planning application.

However, anyone living in a designated area, such as a Conservation Area, Area of Outstanding Natural Beauty or National Park will normally be required to gain planning permission. If you live in a listed building you will need to seek Listed Building Consent.

It is also wise to contact your local authority to check whether there are any planning conditions attached to your home. Sometimes restrictions were put in place when a property was constructed, meaning that the garage has to be retained as a place to park. In this instance, you’ll need to submit an application to have the restriction removed.

A lawful development certificate is highly recommended. While not a legal requirement, this certificate will confirm to both you, the local authority, and any future buyers of your property that your garage conversion was carried out in accordance with the correct planning procedures. If you are carrying out a garage conversion under permitted development, a lawful development certificate is particularly worthwhile. There are certain conditions surrounding permitted development – details of which can be found in our Beginner’s Guide to Planning Permission – which need to be met to ensure your conversion qualifies.

If you are converting a detached garage, as opposed to an integral one, you are more likely to require planning permission, or need to apply for a change of use. A planning permission application might also be required if you plan on making significant changes to the appearance of the garage, such as extending it, raising the roofline or introducing larger areas of glazing. 

Planning a garage conversion

Once you dive into your garage conversion planning you will find there are several issues to consider and talk through with your builder. This will help you get an idea of your garage’s potential, ensure that the timescale is realistic, and enable your builder to give you an accurate quote.

Garage conversion: structural integrity

One of the first steps you need to take in your garage conversion planning is to look at the existing structure. You should consult a builder who has experience of the type of garage conversion you are carrying out. You might also want to speak to a structural engineer.

The walls, foundations, and floors will all need to be assessed before you can get an idea of the viability and likely costs of your conversion.

One of the main ways a garage is integrated into the rest of the house involves blocking up the old garage door opening — often replacing it with a window, full height glazing, or a new doorway.

Before this can be done, it is vital to check that the garage’s existing foundations are up to the job of supporting a new wall and any glazing. That often means digging small trial holes in front of the concrete slab in order to check its depth, which should be 200mm or more, to provide adequate support for a new brickwork wall.

There are two possible solutions if the foundations are not up to scratch.

  • The first is to excavate a 1m footing wall which is then filled with concrete.
  • The second is to add a 140mm x 100mm concrete lintel to the new wall, below ground level, on either side. The new wall can then be constructed.

Your builder will be able to fully advise you on which route you should take. For two-storey garage conversions, it is very often necessary to reinforce the existing foundations — again, the services of a good builder here cannot be emphasised enough.

Garage conversion: insulation

Garages were not originally built to provide a comfortable living environment and so are unlikely to be sufficiently insulated. The Building Regulations also require your conversion to meet certain thermal regulations.

There are several different ways in which garage conversion insulation can be added and your builder will be able to talk you through them.

The easiest way to insulate a garage is to use insulated plasterboard. This is fixed to timber battens, with a damp proof course (DPC) positioned between the batten and the wall. The other option is to place insulation between battens with a fireproof plasterboard over the top.

If your garage conversion is to be two-storey, or already has a room above it, it is unlikely you will need to think about roof insulation. However, with single storey garages, it will need to be a consideration.

Your builder will advise you on garage floor and roof insulation. Most garage floors will be lower than those in the house, so by adding a damp proof membrane, insulation, screed and your chosen final floor finish, the floor will usually come up to a similar level.

Garage conversion: heating, plumbing and electrics

Depending on how your garage conversion space will be used, it may be necessary to incorporate new heating, plumbing and electrics. The best way of doing this is to find tradespeople who can self-certify their works to comply with the Building Regulations. Your builder may be able to liaise with the required trades for you under a project management role.

Garage conversion: electrics

It is sometimes possible to connect the garage to the household mains consumer unit but, depending on what you are including in your conversion, it may be necessary for the consumer unit to be upgraded or replaced in order to cope with the additional strain.

Your builder or electrician may suggest installing an additional mains supply and separate consumer unit. Alternatively, it may be possible to put the garage on the existing consumer unit but with its own miniature circuit breaker (MCB).

For detached garage conversions, wiring from the mains consumer unit can be run underground from the main house, although it is common for a new connection to be needed. A fully qualified electrician will be able to advise you, and you can find one using our Find a Builder tool. 

Garage conversion: plumbing

If you want to locate a new toilet or bathroom facilities in your garage conversion you’ll need to consider how to bring water in and how waste water will be taken away. A good plumber or builder will be able to advise you.

Garage conversion: heating

One of the simplest ways to heat a garage conversion is to install a radiator, run off your existing boiler. However, underfloor heating can also be a good solution, leaving walls free and therefore maximising space. 

Your plumber should be able to advise you on whether or not your new plumbing and heating systems will require upgrading your existing boiler. Some people opt for electric radiators instead.

Garage conversion: fire safety 

Part B of the Building Regulations covers fire safety – the Planning Portal website is a useful source of information – although a good builder should be well aware of the regulations that your conversion needs to conform to.

If your garage conversion is accessed by the hallway then this will be seen as providing a safe means of escape to the outside. If, on the other hand, the new room you are creating by converting the garage can only be entered through another inner room (that is one with no direct access to outdoors), it will need an alternative escape route.

If the inner room is a kitchen, en suite, cloakroom, WC or bathroom then an alternative exit will not be required. An escape route is usually provided via a new door or window and is often created by replacing the old garage door.

In the case of partial garage conversions, where only part of the garage is being converted into habitable space, the wall that is built to separate the two areas should be fire-rated to 30 minutes.

Garage conversion: damp-proofing

Although your existing concrete garage floor slab should be adequate as the base for your newly converted space, a damp proof membrane (DPM) may also be installed to stop water coming up through the slab. DPMs come in both solid and liquid forms and insulation will be fitted on top of this.

When it comes to the walls, it is not uncommon to find that a garage has been built using only a single skin of brickwork. For the space to become a comfortable, habitable room, this type of wall usually requires upgrading with a cavity wall to meet insulation requirements.

Where the garage butts up to the outside wall of the house, the wall can become damp. Inserting a cavity tray damp proof course into the wall above the roofline of the abutting buildings can prevent water running down into the cavity of the wall — speak to your builder about the best way of doing this for your individual project.

Garage conversion: replacing a garage door

Unless you are retaining the front portion of your garage as a storage space, the old garage door will need to be replaced with a new wall and usually a window and/or door too (see the note on reinforcing the foundations above).

If you live in a Conservation Area it may be necessary for you to keep the existing garage door in place. While not ideal, there are solutions that can help with this. One is to build a false interior wall behind the garage doors and to use rooflights to bring in natural light.

Garage conversion: replacing a garage roof

The old roof will almost certainly need to be replaced or upgraded to make a garage conversion fully watertight. Your builder will be able to advise you on your options for choosing new tiles or another roof covering — aim to match those on the existing roof where possible.

Many people opt to swap the old flat roof for a pitched one in order to enhance the visual appeal of the conversion. A new pitched roof is also the ideal spot for a couple of new rooflights. This option may require planning approval, so be sure to check before making any changes.

Do I need a designer?

'Do I need a designer for a garage conversion?' is one of the key questions many people will ask when starting this type of project. The answer is that there are actually various routes you can take when it comes to designing your garage conversion. The right choice for you will depend on the scale and complexity of your project, as well as your budget. Here’s a quick guide to your options:

 

Architect

Using an architect, professional designer or architectural technician is a great route for substantial garage conversions, where there are perhaps multiple planning stipulations to be followed as can be the case in designated areas such as Conservation Areas and Areas of Outstanding Natural Beauty, or where Listed Building Consent is required.

An architect can also be useful where you need assistance with the design, or when the roof is being replaced. A good architect or designer, with experience of your type of project, and who comes with recommendations from trusted sources, will also be useful in providing contacts with other trades and should have an in-depth knowledge of the building regulations.

Builder

Choose a builder who comes with recommendations from people who have carried out similar projects to yours, and ideally who is a member of the FMB. It does help if you have some ideas for how you want the new space to look. This will enable your builder to understand what you hope to achieve and also to provide you with an accurate quote.

Design and build

Choosing either a design and build company or a garage conversion specialist means that all the legwork involved in finding trades, getting a design drawn up, and project managing the conversion is done for you. This might not be the cheapest option, but it is often one of the simplest. A good package supplier should also have plenty of experience in dealing with planning issues, building control and the very particular issues that are part and parcel of garage conversions. 

DIY

Those on a tight budget sometimes choose to formulate their own design. However, while this may save money upfront, be aware that you need to be completely clear with your builder about your brief in order for the project to run smoothly and to help them quote accurately. It is often worth asking a draughtsperson or house design professional to translate your own ideas into technical drawings to ensure accurate quotes and also for building regulations purposes.

Finding a builder for your garage conversion 

You’ll need to source a quality builder or garage conversion specialist to ensure the conversion is well done. Consider using the free Find a Builder tool to choose an FMB member. That way you can be sure you will find an expert who has been professionally vetted and independently inspected on joining the UK’s largest trade association for the construction industry. 

You can find out more about selecting the right builder in our How to Choose a Builder guide, although do get a minimum of three quotes from separate builders before you make your final decision.

What building regulations do I need to consider?

A garage conversion is classed as a change of use, so it’s essential that your project complies with current building regulations. This is your responsibility, but your builder should be well aware of which regulations will apply, and your local building control department will also be able to provide you with full details.

Garage conversion building regulations apply to:

  • Fire safety: escape routes and fireproofing must be put in place.
  • Ventilation: moisture proofing and good ventilation is essential.
  • Thermal performance: floor, wall and loft insulation is required.
  • Acoustics: soundproofing will be necessary.
  • Electrics: certain electrical work must only be carried out by a suitably qualified electrician.
  • Structural concerns: foundations will need to be assessed and reinforced where necessary.

You will need to submit a building notice or full plans application to your local building control office. A building control officer will then visit to inspect the project at various stages as the conversion progresses. The inspector will check the work complies and then issue you with a final certificate on completion.

More detail can be found in our guide to building regulations.

If your garage conversion is likely to affect any shared walls, structures or fences with an adjoining property, the Party Wall Act will apply. You can find out more in our guide to Party Wall Agreements.

How long does a garage conversion take?

The timeline will be affected by the individual complexity and scale of your project. You can expect things to take longer if considerable structural work is needed to reinforce foundations, or if you have to wait for planning permission to be granted. The timeline will also depend on how you intend to use your garage conversion — a kitchen installation will take longer than a playroom, for example.

Typical Schedule of Works for converting a garage

  1. Investigate whether your garage is suitable for conversion.
  2. Check whether planning permission will be required.
  3. Get plans in place for a design.
  4. Apply for planning consent if necessary.
  5. Ask your builder, architect or design and build company to produce detailed design and building regulations drawings.
  6. Be sure to contact your insurance company to arrange cover for the works and the existing structure.
  7. Let Building Control know that work is commencing.
  8. Strip the existing garage back to the structure you are retaining.
  9. Make structural alterations, such as knocking through to the house or alterations to the roof.
  10. Damp-proof the floor.
  11. Insulate walls and floor — as well as the roof if the conversion is single storey.
  12. Fit underfloor heating if required.
  13. Pour floor screed.
  14. Install windows and doors.
  15. First fix electrics, plumbing and joinery.
  16. Plasterboarding and plastering.
  17. Fit new internal doors, mouldings (skirting etc), final floor covering and lights.
  18. Decoration.

If you are converting your garage into a kitchen or bathroom, additional work will be required and the project will take longer to complete. Make your builder fully aware of your plans for the new space from the outset and then they can factor in all the necessary works.

Do I need insurance for a garage conversion?

You should arrange conversion insurance if you intend to project manage the garage conversion yourself. You may not be covered for loss or damage that could be caused by the work if you do not have adequate cover in place. Conversion insurance should cover the work carried out as well as your house. In addition, materials, tools and equipment will also require cover. Public liability and employer’s liability should be included too.

If you are using a builder, then they should have their own insurance to cover the conversion, but do check with them before work commences. You can contact FMB Insurance if you have any questions about the type of cover that is appropriate for your project.

 

Garage conversion cost

Garage conversion costs can vary hugely depending on the particular specs of your project, including how you plan to use the space (e.g. a kitchen conversion will cost more than a simple playroom), where you live in the UK, and the quality of fittings and finish you would like. Because no two projects are alike, it’s better to develop as detailed a brief as you can for your builder than to focus too heavily on generalised online pricing guides.

The main factors that will affect your garage conversion cost are: 

  • Foundations that require reinforcement.
  • A ceiling that needs to be raised. Bear in mind that a height of 2.2m-2.4m is required once the old floor level has been raised so that it’s 15cm above the external ground level.
  • Design fees.
  • Planning application or party wall agreements.
  • Structural engineer fees.
  • Walls, floors or a roof structure requiring substantial repair.
  • What you include in your conversion e.g. a kitchen or bathroom. 
  • Underfloor heating.
  • Whether or not the garage is integral, attached or detached.
  • The level of insulation required — if there is to be a new room above, for example, ceiling insulation requirements will be different.

Check what your garage conversion quote includes:

Ensure you’re comparing apples-to-apples with your different quotes by checking whether your builder has included the following costs:

  • Design fees.

  • Upgrading electrics (for example, adding an additional mains supply or separate consumer unit).

  • Structural engineer.

  • New flooring.

  • Plaster or plasterboard walls, along with paint.

  • New boiler (if required).

  • Plumber to extend heating system.

  • Certificate of lawful development in England.

  • Full planning permission application in England.

  • Party wall agreement.

  • Building regulations fees.

Full details of planning permission and building regulations fees elsewhere in the UK can be found in our guide to building regulations

Don’t forget to factor in VAT too. Always ask your builder if there are any other costs that you need to account for which are not included in their quote. Our find a builder article has more on choosing your builder and ensuring an accurate quote. A minimum of three quotes will help you to weed out any responses which are unrealistically expensive or, just as bad, too cheap. 

For more information on planning permission and regulations for garage conversions, see the LABC’s Front Door website.

You may also be interested in

How to choose a builder

Whether you are building a new home from scratch, carrying out renovation work or having a new extension built, you are going to need to find a builder to carry out the work. But just where do you find the best builders for your project?

Working with your builder

A successful building project relies on a good working partnership and open communication between you and your builder.

Why choose a Master Builder?

Our strict membership criteria, unique vetting and inspection process gives homeowners confidence when looking for a quality, professional builder.