How to convert a garage: the ultimate guide

A garage conversion is a cost-effective solution for those who want more space without needing to extend. Find out how to successfully convert a garage into extra living space

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A garage conversion can add up to 10 per cent to the value of your home and give you valuable extra living space that's less prone to planning complications. Better still, it's significantly cheaper than building a new extension – expect to pay anything from £5,000 upwards – and much more affordable than moving house. 

Plus, if have a double garage, you could convert just half the space, so that you gain living space and continue to benefit from a parking space.

What to consider before you convert your garage

First, consult an estate agent about whether converting your garage could have a negative impact on your property's price. If you'll be living in your home for years to come, it may well be worth proceeding whatever they say, but if garages are highly sought after in your area, think carefully before converting yours.

Before you start work on the conversion, consider what you’ll do with everything currently kept in the garage. If you store a lot of garden gear in it, you may need to factor a shed into your plans; if it’s where you keep your chest freezer, you’ll need to work out where it can be moved to – or whether you can live without it. If you really have no room anywhere else for these things, perhaps a partial garage conversion (or a conversion that has lots of storage space set aside within it) will work better for you.

Related articles: Before and after design ideas for garage conversions | 7 ways to create more usable space indoors without extending | 12 garage storage ideas

How much does a garage conversion cost?

The upside to converting an existing garage is that you will save money on laying new foundations and building new walls; your garage may also have power and perhaps even plumbing already, both of which will reduce your garage conversion’s cost even more.

So, how much will a garage conversion cost? You can expect to pay between £5,000 and £7,000 upwards (depending on spec); that's around £1,000 to £1,250 per square metre – if the walls and floor are stable, there is a watertight roof, and the ceiling height is sufficient to leave around 2.2m to 2.4m of headroom after building up the floor by 15cm above external ground level. 

If the structure is attached to the house, rather than integral, and needs structural repairs, it may be more cost-effective to demolish and replace it.

Compared to the cost of a single storey extension, which will be upwards of £13,000, it's a cost-effective way to gain more space indoors.

Design costs

Design fees for a garage conversion range from £1,200 to £2,500, plus £300 to £400 for a structural engineer. A typical single garage conversion (18 square metres) could cost as little as £5,000 without fitting costs, but expect to pay around £17,100 to £23,900; for a double (36 square metres), £31,300 to £43,300, plus VAT, is more likely, depending on personal specifications.

Factors that might affect garage conversion costs

Typically, a garage conversion will cost more if the original structure is unsound. If you are going to spend a lot of money stabilising the building, knocking the original garage down and building from scratch might be cheaper.

Another factor to consider when costing a garage conversion is the perceived value that it will add to your home. Check the value of houses in your area, if there is little off-road parking, homes with garages might be valued higher than those without. Unless the added space is vital, don’t run the risk of reducing the value of your own home.

A partial garage conversion should cost less, but not by much. Fewer materials will be needed, but services, such as electrics and plumbing, will still have to be installed and budgeted for.

Dining area with Philip Starck Ghost Chairs in a converted garage

Part of this former garage has been transformed into a dining room that opens on to the outdoor space

(Image: © ZazuDesigns)

Planning permission for garage conversions

In the majority of cases, the work involved in converting a garage will be classed as permitted development. However, if you live in a Conservation Area, a location where development can be restricted to protect the appearance of the surroundings, or on a new estate with strict guidelines (some new homes are built with a condition that the garage remains as parking, so you'd need to apply to change its use), it’s worth checking what’s allowed. Detached garages are much more likely to require planning permission for a change of use.

If in doubt, apply for a certificate of lawful development from your local authority at a cost of £86. Do remember, the removal of permitted development does not rule out the potential of a garage conversion, but you’ll need to ensure the design is sensitive to the setting and apply for full planning permission, which costs £172 in England. Listed properties will need listed building consent, too.

When you will need planning permission:

  • If you live in a listed building;
  • If the garage conversion increases your home beyond permitted development rights;
  • You are converting the space for business;
  • Your council has restrictions on reducing parking.

Even if these restrictions apply, you should be able to convert the garage interior as long as the exterior is untouched.

a conversion of a integral garage

Berry Construction converted an integral garage in London into a valuable double bedroom (which can be seen below) with en suite shower. The project cost around £40,000

(Image: © Berry Construction)

Don’t forget building regulations approval

As a ‘change of use’, a conversion is subject to building regulations approval, so your local authority will need to be notified. But you’ll need building regulations consent and sign off for the various elements of your garage conversion, as with other home alterations. To comply, it must: 

  • Be structurally sound and have a damp-proof course. 
  • Have the walls, the floor and the roof insulated to be energy efficient. 
  • Have all new and existing electrics tested to ensure safety. Future-proof the space by allowing plenty of electrical points and a phone point, even if they won’t be used now.
  • Be moisture proofed, with good ventilation. 
  • Fire-proofed, with escape routes (in case of fire), that comply too.

Once the building inspector is satisfied, the completion certificate will follow within 28 days. You can use the council’s building control service or an approved independent inspector, costing around £300. Always check that your local council is happy with your plans before starting work. For details, see planningportal.gov.uk.

Other permissions

Sometimes there are legal restrictions on alterations to a property, so check the deeds to your home to see if permission is required from a previous owner. If the work affects a structure shared with an adjoining property, the Party Wall act will also apply. Expect to pay around £700 to £1,000 for a party wall agreement with your neighbours – although if you are able to persuade them to sign a waiver, you'll save yourself this cost.

Dining room in a garage conversion

This open plan kitchen diner was once a garage beneath a pretty coach house in Devon. To see the exterior, take a look at the image at the top of the page

Garage conversion design details

Making a garage conversion look like a natural part of your home, and less like a converted garage, is vital for its success and your home’s future saleability. Before work starts, commission scaled drawings of the finished project, indoors and out, and include details such as power sockets and furniture layout. Consider these points:

Exterior

‘Ensure the brickwork, materials and windows replacing the garage door match well with the existing house,’ says Jeremy Leaf, estate agent and chartered surveyor. ‘Ask builders to fully tooth and bond the new brickwork into the old.’

‘Often, the top of the garage door is lower in height than the other doors and windows on the ground floor. Consider whether you will be able to match the brickwork or external materials if the garage door opening requires reducing in size,’ advises Designer Nigel Lewis of Space & Style Home Design (spaceandstyle.co.uk).

Floor levels and flooring

‘The garage floor will usually be lower than the floor level in the existing house,’ continues Jeremy Leaf. ‘So do try to avoid a step down into the room and raise the floor if the ceiling height allows.’ Whatever your flooring – whether carpet or tiles – you will likely need a new concrete sub floor poured first; this will add to your costs by around £1,000.

Access

Design the position of the door to the new room in the right place. ‘It’s best to consider what the ideal position would be, rather than going with the existing door if there is one,’ says Nigel Lewis. Work out how the door’s position will affect the furnishing of the new room — it’s no use positioning it in an ideal place in the hallway if it makes the new room awkward.

Natural daylight

If you can fit in extra windows to make the new space feel more like a room and less like a conversion, do so. If the garage faces into the garden, replacing one wall with floor-to-ceiling windows or folding-sliding doors will make it feel wider and much more spacious, but do consider how this will restrict the layout of the room. A door or window will cost upwards of £500 to £600; expect to pay more for bespoke and high quality finishes.

Decorating details

Match the decorating basics to the rest of the house, but particularly to the room adjoining the conversion. This means sourcing (or having made) similar windows, doors and fittings, skirting, flooring and light fittings.

Room proportions

Typically 5m x 2m inside, a converted garage may feel somewhat long and narrow. You can correct this by building a stud or block wall to convert the garage into two spaces, perhaps a boot room, a cloakroom or a utility room.

You can visually change the proportions of the room by using paint colours that make it feel bigger and brighter, too. Keep windows uncluttered, and hang mirrors to reflect light and stretch the space visually. Shop for furniture that matches the room’s proportions; if it’s too big, the room will feel cluttered. Invest in good storage, too.

spare bedroom in a garage conversion

Converting an unused garage in a high value area such as London and adding extra living space can be a sure way of adding significant value

Architect or garage conversion specialist?

Using an architectural designer or a specialist garage design and build contractor, will help put your ideas into fully formed plans, and give you much needed expert design input. If the garage is attached or integral to your home, they will also help you consider the best position for access, and put plans in place to redirect this if required. 

To find an architect, visit architecture.com or use an architectural technologist (see ciat.org.uk). The starting point for your design is to draw up a floorplan. Expect to pay from as little as £1,200 right up to £3,000 for an architect's services, depending on the complexity of the design.

Specialist garage conversion companies can save you time in putting together applications and will be experienced in getting the best from this type of project, but any good builder will be able to do the job. 

Ideally, work with someone who has been recommended and is a member of an accredited body, such as The Federation of Master Builders.

Can you DIY a garage conversion?

Some people choose to come up with a design themselves and carry out all the work they can on a DIY basis – a good option for those with limited funds and the spare time to get stuck in.

You can do most of the garage conversion yourself, which is ideal if you’re on a tight budget, but your work will be regularly inspected by building control officers and anything that’s not up to scratch will have to be undone at your own expense.

Get written quotes (not estimates) from three different companies, with a clear specification of what’s included. Using an architect can give a more creative result.

home office with furniture from The Dormy House

A converted garage can create the perfect space for a home office, as this office furnished with items from The Dormy House shows

(Image: © The Dormy House)

Garage conversion structural essentials

  • Replacing the door: The garage door will have to be replaced with a new wall and/or window. This may mean new foundations, but there are other options, including having lintels set just below ground level that bear on sound masonry or existing foundations each end. Expect to pay, including a small window, around £1,300 for this.
  • Upgrading the roof: The garage roof will almost certainly need to be upgraded to ensure it is water-tight. Use new tiles and materials that match those of the main roof. If you can swap a flat roof for a pitched one it will make the conversion less obvious from outside, and the new raised pitch may have space for rooflights. Doing much more than general repairs to the roof will have to be approved by your local building control department.
  • Internal wall work: An internal structure of stud walls built inside your garage will have insulation added to increase energy efficiency. Expect to pay around £750 per stud wall.
  • External garage walls will usually be single course brickwork, which won’t meet building regulations for moisture and insulation. This can be solved by adding an interior, insulated stud wall built off a damp-proof course on a couple of courses of bricks. ‘Set 75mm clear of the original wall, this stud wall can easily accommodate services and insulation prior to plasterboarding,’ says Designer Nigel Lewis of Space & Style Home Design.

a garage converted into a bedroom with Ikea furniture

If your garage is in a garden and does not face the road, you can easily convert it into an annexe or bedroom for guests or a teen. This eclectic room, furnished with items from Ikea has been fitted with Belgian-style doors, flooding it with natural light

(Image: © Ikea)

Ventilating, heating and insulating a garage conversion

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Ventilation

Shower rooms and kitchens must meet building regulation requirements with extractor fans, but you might also like to include an extractor if you’re planning on using the room as a home gym. Otherwise, an opening window and background ventilation in the form of air bricks or trickle vents will be needed.

Insulation

Building regulations require walls, windows, the floor and roof to be insulated to a certain level. It’s important to get this right — poorly done, it will result in a cold, damp room. 

With pitched roofs, insulation may be two layers of 150mm glass fibre quilt, one between the joists, another over; flat roofs tend to need one layer between the joists of rigid PUR insulation board and another below, with a 50mm air gap above for ventilation. The second layer underneath will drop the ceiling height, however. 

Dry-lining the walls and fitting sealed double-glazed windows are also probable requirements. New windows won’t usually need planning permission but will need to be energy-efficient and double-glazed to be approved by building control. They may also need to be able to be opened right up, too, to comply with fire safety regulations (see above). Match the style to the house’s existing windows to help the conversion fit in.

If floor height is an issue (particularly if you've had to lower the ceiling to insulate it, fitting multi-foil laminate insulants rather than using polystyrene floor insulation can help reduce the thickness of the under layer. 

Heating

If your boiler won’t cope with another radiator, or it’s not practical to run the new pipework, consider electric underfloor heating, which is relatively easy to install.

Bear in mind that bedrooms, home offices and playrooms will need more insulation and better heating than a utility room, while a home gym or shower room will need better ventilation than a living room.

Electrics and plumbing in a garage conversion

Plumbing

If you're planning on installing a toilet or shower, double check the location of the existing water and soil pipes – doing so may help you keep garage conversion costs down, if you can put your fittings in a convenient place. 

Bear in mind the extra costs involved in installing a radiator – and the extra strain put on your boiler. Factor in between £1,000 and £3,000 for gas and plumbing works.

Electrics

Ask your electrician or builder if rewiring the garage for lights and electric radiators will mean that your mains (fused at 100 amps) will be put under strain, too. They may suggest installing an additional mains supply and separate consumer unit, which can add significantly to garage conversion costs. 

Another option is to put the garage on the existing consumer unit, perhaps with its own miniature circuit breaker. Consider adding a minimum of one new 20-amp circuit, too.

If yours is a detached garage conversion, wiring can be run through an underground conduit, although a new connection may be needed if it is to be a separate dwelling, an annexe, perhaps. A good electrician will always be able to advise.

Expect to pay around £100 to have a new electrical socket fitted; this price will be negotiable the more electrical work you are having done.

9 ways to use a garage conversion

When building a garage conversion, how you use the new room will depend not only on your needs but also on how the space relates to the rest of the house. So, if your garage is joined to your living room, a home office or playroom is sensible, and a utility less so. Here’s how you could use the room, with a few pros and cons.

1. Kitchen-diner extension

If your garage adjoins your kitchen, knocking through into the space to create a bigger, brighter kitchen-diner will give the best results in terms of usefulness and financial investment. If you do this, be prepared to plan very carefully to get the design details right. It’s vital that the new room doesn’t have the feel of a boxy converted garage. Need inspiration? Check out this former garage converted into a gorgeous kitchen diner.

2. Extra living room

If your family is growing (or growing up), you’ll begin to need extra living space to cater to everyone’s tastes and needs. A converted garage that your kids can use – whether for gaming, relaxing or entertaining their friends – will be invaluable. Kit it out with plenty of slouchy seating (sofa beds will be particularly useful) and a TV to create a versatile space that they’ll gravitate towards. The downside? The older children become, the noisier they get, so ensure that the sound-proofing is up to the job.

3. Utility room

When a garage adjoins a kitchen or hallway, it will be very useful as a utility room. Use it for everything from laundry to extra storage and, if possible, squeeze in a downstairs cloakroom, too. Depending on your needs, you might even be able to devote half of a large garage to utility and leave the other half for a car. Or, you could split the room to create half utility, half playroom, for example. For a utility, underfloor heating will be useful for keeping the room warm and dry, while good ventilation is also a must.

4. Extra bedroom

With a small garage off a living space or hallway, converting it into a spare bedroom for guests will be a good idea, but the room will be much more practical if you swap a conventional bed for a wall bed or sofa bed and fit in a desk or exercise space to double the functionality. The downside to a downstairs guest bedroom might be lack of access to a toilet or shower room. So, if there is enough room, squeeze in a space-saving wet room.

5. Home office

A home office is best sited away from the main living space if you have a family who will want the TV on while you try to work. If, however, it doubles up as a homework space, having it near to where you’ll be most of the time can be very useful. It will need plenty of natural daylight to make it welcoming during the day, but invest in good blinds if it is south-facing, and ensure the heating is sufficient.

6. Playroom

For a garage off a kitchen-diner or living space, this is the perfect use for families with young children. Include a TV, too, to help keep your living room much more of an adult space. Good daylight, ventilation and lots of practical storage will all be must-haves. Bear in mind that children grow up very quickly, so when you’re converting for this purpose, think five or 10 years ahead to how you might use the room then, too. For example, a teenage den will keep your living room just for you.

7. Home cinema

Perfect for partially converted garages, these rooms can be created without the need for windows, although sound-proofing must be good. Future-proof the room by installing a window anyway and fitting good blackout blinds.

8. Home gym

Ideal for a room that leads off a hallway or kitchen, a home gym will need to be fitted with air conditioning or a window that can be opened to keep it fresh. Add a flatscreen TV and mirrors to make it feel like a real gym, and devote the back of the room to a shower space.

9. Granny annexe

This type of conversion is best suited to an unattached, probably double, garage because it will give both you and the occupant – whether an ageing relative or regular guests – privacy and space. Depending on your arrangements, you will have to fit in an en suite, possibly a laundry room and kitchen, plus a generous bedroom/living space. The room will need lots of natural light, and you should consider how it will be joined, if at all, to the rest of the house. At the very least, you might want a covered walkway between the two buildings.

garage conversion turned in to a garden office

Paul Day of PD Architecture turned his detached garage in to a home office for his practice

(Image: © PD Architecture)

Garage conversion build schedule

  • Check structure is suitable for conversion
  • Produce design drawings
  • Confirm whether planning permission is required
  • Apply if consent is required
  • Produce detailed design and building regulations drawings
  • Arrange conversion insurance to cover the new works and the existing structure; most home insurers will exclude loss or damage while the property is undergoing alteration or renovation.
  • Notify local authority Building Control of commencement
  • Strip garage back to retained structure
  • Structural alterations, including knocking through to house
  • Damp-proof new floor, if necessary
  • Insulate walls and new floor, plus the roof if single storey
  • Pour new floor, if required
  • Install new window and doors
  • First fix joinery, wiring and plumbing
  • Plaster and dry-line
  • Fit new doors, skirting, architrave, fixed floor finishes and light fittings
  • Decorate

Kitchen diner in a garage conversion

This garage conversion is now a spacious kitchen diner

(Image: © Clear Architects)

Fire safety and integral garages

What if you have an integral garage but without an internal door to it from the house. Can you fit one if you're not converting it?

The answer is yes, but two fire safety requirements apply:

The door needs to be an FD30S fire door with a self-closing device fitted. Thirty-minute fire-resisting doors are best bought as a set with the frame because the latter is made from thicker timber than standard and is rebated to fit the necessary intumescent (which means it swells when heated) smoke seal to the sides and the head. Hence, you can’t use normal door frames for this purpose.

Internal doors to garages are the only doors in homes that need to be self-closing. Those with a checking action that pauses in the almost-shut position before fully closing are best, avoiding crushed fingers. The floor within the garage must be at least 10cm lower than the finished floor within the house to prevent fuel spillage running into the house. If it isn’t 10cm lower, the door sill will need to be raised by brick or concrete block to create this 10cm step over, or the floor of the garage should be sloping outwards to beneath the garage car doors.

More ways to make the most of your garage: