Garage Conversions: The Ultimate Guide to Design, Planning & Costs

Garage conversions are one of the speediest and most affordable routes to adding flexible floor space to your existing home. The process will significantly enhance your home’s value and a garage conversion will offer a versatile new space that can be used as a home office, bedroom or home gyms or even a small guest room complete with bathroom and kitchenette.

The ways that garage conversions can be used are endless, but ensuring you’re creating a successful design from the beginning will be key to the overall look, comfortability and longevity of the newly converted space. This will require you to address any insulation upgrades and fit proper ventilation to make sure the new zone can be enjoyed and used all year round. You may also need to incorporate new electrical outlets, windows or accessibility features as part of the redesign.

Before setting out on a garage conversion project, you should consult your local planning authority. While most garage conversions won’t require formal planning permission – as the work will mostly affect the interior spaces – your home’s location will influence the changes you can make. And, as a conversion involves a change of use from garage to residential space, you’ll need to ensure your project is meeting Building Regulations.

If you’re looking to alter the garage’s exterior features such as the windows, you’ll need to submit a planning application as this will end up changing how your home looks. You could always consider a pre-planning application to ensure your garage conversion project is on the right track for success.

Drawing up a Design for Your Garage Conversion

The first place to start with all garage conversions is conducting an assessment of the existing structure, in particular the soundness of the foundations, walls and roof.

This will go a long way to revealing the extent of works required to create a comfortable living environment – so it’s a key part of the early design stages that’ll dictate what you’re able to do with the design later on. If the garage you’re converting is in an especially dilapidated state, it may be cheaper to knock down and replace the structure with a newly-built, efficient version. By doing this you’ll have the opportunity to specify features such as sustainable insulation or a proper ventilation system.

Garage conversions require careful designing to find the right result. The project’s details will depend on the scale of the scheme, how you want to use it and integrate it into the property, and what your budget will stretch to. Speak to a design professional as they’ll be able to help you decide on a project route that best maximises your cash before you can begin designing a high-spec scheme.

For higher-end garage conversions, working with an architect could help to identify creative ways to maximise the potential of your garage conversion and establish a space that flows naturally into your home. Consider how you’ll want to use the space and how frequently, too, as this should help you decide how much of an investment your garage conversion will be.

Another popular route is to use a design and build company that specialises in converting garages. The results can be fantastic and many will take your scheme through planning and building control as part of their fee. Plus, their experience on-the-ground can help to ensure a smooth project and a predictable budget that you can see through to the end.

Read More: 10 Top Tips For Building a Garage: Planning, Costs & Design

This residential garage conversion development project by MW Architects involved converting a set of old coach houses, with the garage on the lower storey transformed into comfortable, liveable homes. Photo: Taran Wilkhu

If your garage is integrated or attached, the space should be fairly easy to work into your home’s main structure and accommodation. You could knock through the wall to join up with an existing zone, for instance – perhaps enlarging a hallway or creating a front-to-back kitchen-diner.

MW Architects‘ coach house garage conversion features a light-filled interior, with the garage-looking front retained on both inside and out to bring the initial structure’s character into the modern day. Photo: Taran Wilkhu

A detached garage, meanwhile, lends itself to segregated uses, such as an annex or quiet home office. A single garage will offer around 15m2 of floor space; more than enough for a new living space, separate playroom, guest bedroom, or even an accessible downstairs shower and WC.

At around 30m², double garage conversions will give you more flexibility. It could house a bigger living room, ensuite bedroom, well-sized kitchen-diner or an annex. Alternatively, you could retain a single parking space inside your garage by erecting a suitably insulated and fire-rated partition, and then fitting out the rest of the room for habitation.

Learn More: Garden Offices: Your Complete Guide to Building an Office in Your Garden

Do Garage Conversions Require Planning Permission?

With many garage conversions – particularly when dealing with integral garages – most of the conversion work will be internal. The main external changes are like to be upgrading the exterior cladding and adding a window or two – think about which materials may complement your home best, such as slim-profile brick slips or timber cladding for a design statement.

The large double doors on this London garage conversion help to maintain a n authentic garage-style look from the street

Straightforward garage conversions like this are often considered permitted development (PD), so won’t usually need formal planning consent.

In some cases, such as in conservation areas, PD rights for a change of use from garage to residential may have been removed. So, consult the local authority before you begin. For peace of mind, you could apply for a lawful development certificate.

In addition, some houses built in more recent times are subject to restrictive covenants, which may require the garage to be retained as parking rather than converting it completely.

Part of a London mews house, this garage conversion has been opened up to the rest of the ground floor – providing space for a stunning kitchen by Cue & Co leading through to a family room and courtyard garden

Before you can go ahead with a garage conversion, any such covenant would need to be discharged (usually for a small fee). Check the title deeds to find out if this applies. In this scenario, you’re also more likely to need formal permission to change the use of a detached garage.

You may still be able to convert a garage into a room even if PD rights have been removed – but you’ll need to put together suitable drawings and apply for householder planning consent. As of December 2023, householder planning applications cost £258, plus any design fees.

A full application will also be necessary if you want to significantly alter the external appearance, such as making big changes to the windows, using new materials or adding an extension. Among the other permissions you might need to secure are listed building consent (if you live in a listed building) and party wall agreements with any adjoining neighbours. Full planning applications cost £578.

Garage conversions usually don’t require planning permission, see 23 other Home Improvement Projects You Can Do Without Planning Permission

Does My Garage Conversion Need a Building Regulations Approval?

As this type of project involves a change of use, a garage conversion will always be subject to the Building Regulations.

For straightforward garage conversions, the building notice route may be sufficient. This is where you or the contractor simply informs the local authority of your intent to start work 48 hours prior to commencing on site. With a building notice, you don’t have to submit structural drawings for scrutiny.

With more complex garage conversions, you may prefer to have full structural plans drafted. This gives you peace of mind that building control has inspected the drawings and confirmed that – if it’s constructed as per the approved schematics – your conversion will conform to the regs.

In addition to structural safety, key areas your building control officer or approved inspector will look at are damp proofing, ventilation, insulation and energy efficiency, fire safety (including escape routes), electrics and plumbing. These are all essential for a good-quality garage conversion that will be safe and feel comfortable.

What are the Key Building Stages of a Garage Conversion Project

Before a garage conversion project can start in earnest, the walls and roof must be made sound and watertight. Thereafter, most of the work will take place inside the existing garage.

The first job will be stripping out the main structure, at which point you’ll get the clearest view yet of what’s in store – including where you’re most likely to encounter unexpected problems (such as patchy foundations or hidden issues in the walls) that could add to costs.

Here are the Key Considerations for a Garage Conversion:

Foundations & Floor Slab for Garage Conversions

When it comes to beginning a garage conversion, a key first step is to investigate whether the existing garage’s foundations need upgrading to take the new loads post-conversion. This will be particularly important if you’re adding new doors or windows as part of the garage conversion.

This is usually done by digging trial pits. If the foundations are at least 200mm deep, they should be able to cope with the loads of a converted garage. If not, or your structural engineer says otherwise, they may need additional support (for instance by underpinning).

An existing concrete garage floor might well be strong enough to cope with general domestic use. However, it may need to be levelled (consider a self-levelling liquid screed), damp-proofed with a suitable membrane (lapping into the walls’ DPC) and insulated to achieve adequate thermal performance.

Garage floors tend to be lower than those in the main house, so it may be possible to incorporate all of this and still achieve a step-free threshold between the two zones.

Here is a garage conversion project getting underway, with alterations made to the original structure as a the old space is converted into a liveable zone