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How Much Does a Garage Conversion Cost in 2023?


Last year I walked into my garage and realised it was full to the brim with old bikes, a broken lawnmower, and a few spare parts to a car that I no longer owned.

After a few days and two skips later, it was completely clear, and I was amazed at how big the space was.

Not wanting to slowly begin filling it back up, I took the plunge and decided to convert it into my new home office.

The office is now finished and it was one of the best decisions I ever made.

The process, however, was more complex than I anticipated.

For those of you in a similar position to me, I thought I’d take some time and prepare a comprehensive guide discussing topics like: How much does a garage conversion cost? What are the best ways to save money? Do you need an architect?

I’ve done my best to answer all the questions which might help you make the decision to convert your garage.

Table of Contents

1. Why should I convert my garage?

Here are a few pros and cons of garage conversions to help you work out if it’s a good option for you:

Increase house price: Garage conversions create more usable space inside your home. We would always expect the increase to the value of your house to be greater than the cost of carrying out the works.

Avoid moving house: One of the most popular reasons for moving house is to gain extra living space. If that space can be achieved by converting your garage, it avoids all the fees you might expect from moving house e.g. removal company, agents’ fees and stamp duty.

Cheaper than an extension: As you’re working within an existing structure, the cost of a garage conversion is usually far less than building an extension to your house.

Lose a parking space: If parking on your street is difficult, then an off-street parking space can be very convenient. Losing it might make it more difficult to find a space close to your house.

Less storage space: Garage spaces are great places to use as storage and for those bits and pieces you don’t want laying around your house. Without it, will you have anywhere to store those things in the future?

A picture of a cosy bedroom garage conversion

2. Are there different types of garage conversion?

There are three different categories of garage conversion:

Attached: This type of garage is an independent structure, but part of the garage relies on the structural support of an adjacent building which would typically be your house.

Integrated: An integrated garage is where your car is parked within the main structure of your house with an integral door leading to the main living space.

Detached: A detached garage is where your car is parked in a separate structure and therefore not connected to your house.

3. Do I need Planning Permission for a garage conversion?

In most instances, if you own your house, you will not require planning permission to convert your garage into a habitable room. There are some exceptions however, which are discussed in more detail below.

Certificate of Lawful Development: If you own a house, the chances are that your garage can be converted into a habitable room without the need for planning permission by using your ‘Permitted Development Rights’. That being said, we would always advise that you apply to your local planning authority for what’s called a ‘Certificate of Lawful Development’ before construction starts. That certificate will confirm that your garage conversion does not require planning permission. This can be useful when selling your house to show future buyers that you have all the relevant permissions for any changes you have carried out over the years.

Planning Permission: There are, however, some cases where you might not have ‘permitted development rights’. These include:

  • You own a flat
  • You live in a Conservation Area
  • Your permitted development rights have been withdrawn
  • You live in a National Park
  • You live in an Area of Outstanding Natural Beauty
  • You live in a World Heritage Site
  • You live in Norfolk or Suffolk Broads

For a more detailed understanding of ‘Permitted Development’, the Planning Portal has a very useful article here.

If you fall into one of the above categories, that does not necessarily mean that you cannot convert your garage. It just means that you would need to apply for planning permission.

Most local planning authorities will have published a document titled ‘Residential Design Guidance’. These are designed for homeowners and explain the specific local design rules for different types of extensions including garage conversions.

The two main considerations when it comes to assessing your garage conversion will be: how does your proposal affect the character of the area? And does the loss of an off-street parking space create increased on-street parking problems?

These are factors your local authority will consider before granting planning permission.

4. How much does an average garage conversion cost?

Garage TypeCost RangeAverage Cost
Integral garage conversion£8,000 – £12,000£10,000
Attached garage conversion£10,000 – £20,000£15,000
Detached garage conversion£15,000 – £25,000£20,000

We appreciate that all garages are very different, and the above costs are ranges and averages.

To help you work out how much your specific garage might cost to convert, we would estimate between £800 and £1,200 per m2.

So, if your garage measures 10m2 you would expect to pay between £8,000 and £12,000.

If you compare this to the cost of an extension, where the range is between £1,500 and £2,500 per m2, it is a far more economical way to gain some much needed extra space.

5. What affects the cost of a garage conversion?

5.1 Architects and professional fees

There are two main options when it comes to choosing a professional to help take you through the design and construction process:

Builder or garage conversion company: As the design and technical work involved in a garage conversion is relatively straightforward, there are a number of builders and specialist companies who will include all their professional fees within the construction cost.

The advantage of this option is that it makes it far easier for you, as there are fewer professionals involved in the process.

The only disadvantage of a builder managing the design and planning process is that there is little incentive for them to keep costs down. It is also worth noting that while a builder’s fee proposal may include a very low fee for the design stage, they will simply add a percentage to the total construction cost to compensate.

Architect: Architects are experts in design, so we always think it’s a good idea to approach one before you start a garage conversion project. Not only will they be best placed to suggest some fantastic design ideas, but they will actively work with you to work within a budget, which a builder won’t be as incentivised to do.

We would expect the total professional fees for a typical garage conversion to range from approximately £1,500 – £3,000, including both the architect’s and engineer’s fees.

A picture of a living room garage conversion with a TV.
A stylish and modern living room garage conversion

5.2. Foundations, walls and windows

Foundations: This depends on the type of garage you have. If you are simply adding windows and a door to the front of your garage, you might not need new foundations. If you need to build a new masonry wall and roof however, then you may require new foundations.

Walls: As above, this very much depends on the state of the existing garage. There are two types of possible wall construction for a garage conversion.

  • Single thickness wall (100mm)
  • Double thickness wall i.e. (cavity wall) 250mm

Double thickness walls offer more insulation and reduce the transfer of noise through the walls. If you want to upgrade from a single to double thickness wall, that might add a little extra to the overall build cost.

Windows: In most cases, the original garage door would be replaced by a window to let as much natural light in as possible. This really does depend on your budget. UPVC windows are relatively inexpensive and could cost approx. £800 per window. Aluminium windows might cost slightly more at approx. £1.000 per window. For the extra money, it’s worth bearing in mind that aluminium windows will last longer than UPVC.

5.3. Flooring

In most cases, the existing floor of a garage will be worn with the occasional crack, meaning it might have to be replaced.

When replacing your floor there are two options. You can either create a wooden frame or pour a new layer of concrete over the existing floor. The advantage of a new concrete floor is that it is often more durable and also gives you the opportunity of including some underfloor heating, which means you take up less space with radiators.

5.4. Insulation

Fix the insulation directly to the wall: If the walls of your garage are in a good condition, this is a relatively inexpensive option. The cost of insulation boards ranges from £10 – £20 per m2. However, the speed of the insulation compensates for this extra cost.

Fix battens to the wall which can carry the insulation: This option is similar in terms of cost to the option above. It is used more when the existing walls are a little uneven, and helps to create a barrier between the wall and the new insulation.

Construct a new stud wall inside the existing wall: Where there are problems with water ingress from the outside, this is the best solution but more expensive than the above two options. Also, it uses up more much needed floor space.

5.5. Electricity

Usually, you will be able to connect your garage conversion to the main consumer unit in the house. Although, your electrician may need to upgrade that unit to handle the additional strain. Depending on the existing arrangement your electrician or builder may suggest installing a new mains supply or maybe a miniature circuit breaker.

5.6. Heating

The quickest and most cost-effective way is to install radiators which can run off your existing boiler. If you have a slightly bigger budget and are having a new concrete floor, underfloor heating is certainly a great option.

A picture of a garage that has been converted to a gym
What better reason to cancel that gym membership by converting you garage into the ultimate workout room

6. Are there ways to save money on a garage conversion?

Save on professional fees: Although hiring an architect can be useful, there is no requirement to use one.

An option to save money on professional fees would be to use a builder or specialist garage conversion company who are able to complete the necessary paperwork and obtain all the relevant consents on your behalf. While you might not get the same creativity and ideas from a builder compared to an architect, their fees for managing the process will probably be less.

Save on Labour: If your existing garage is like mine, it may be full of furniture, old bikes, and an old washing machine, perhaps. If you let the builder know that you will take responsibility for clearing the space before they start, they will certainly reduce their fees accordingly.

Save on Skip Hire: Depending on how full your garage is, you could clear the garage yourself and take anything you don’t need to the tip. Although this might take a few trips, you will then need fewer skips which can be expensive.

Save on decorating fees: The specialist work such as new foundations, walls, utilities and heating can all be completed by your builder. You can ask them to leave you with a completed shell. Depending on your DIY skills, you could then buy some paint, rollers and flooring and finish off the last few bits and pieces. This will also give you the opportunity to add a more personal touch.

Save on finishings: A quick search of Google will no doubt reveal a number of sales where more premium options can be purchased for a fraction of the original retail space. It’s also always a good idea to go into the shops themselves and ask the salespeople if they have any ex-display or discounted items.

7. Why does the price of a garage conversion vary so much?

Every garage is unique and might have its own particular set of challenges which make construction more complicated. Here are a few factors which might affect the cost of your garage conversion:

  • You need new foundations
  • The walls, floor or roof need to be replaced
  • The existing ceiling is too low and needs to be raised
  • You need to apply for planning permission
  • Your garage conversion needs a structural engineer
  • You need to build a new cavity wall

8. The advantage of working with an architect for your garage conversion

The quick answer is ‘no’, there is no legal requirement for an architect to design your garage conversion. But, there are certainly advantages of hiring a design professional such as an architect to help you through the process:

Creativity: A local architect will have worked on hundreds of incredible garage conversions. They will have a huge number of ideas and examples of what might work best for you. They may also show you some modern and unique materials you otherwise might not have considered.

Peace of mind: As all architects are members of the Architects Registration Board, that means they will have a huge amount of experience. They will give you the peace of mind that the construction works will be carried out to a very high standard.

Project management: Although garage conversions are relatively straightforward, managing the design, planning and construction process can be quite time consuming if you haven’t been through the process before. Architects will be able to give advice about planning, and can also recommend good engineers and builders. More importantly, as they will have worked on lots of garage conversions, they will be able to manage the process efficiently to make sure the works are completed quickly. This allows you to use your incredible new space sooner.

Planning expertise: Most garage conversions can be built under permitted development without the need for planning permission. There are however instances where planning permission would be required. A good architect will understand your local planning polices, which will help your application sail through the planning system, avoiding delays.

Quality of the finish: Architects often have very good attention to detail. As part of their service, they can come to site at pre agreed milestones to check that your builder’s work is to a high standard.

Building Regulations: Depending on the complexity of your garage conversion, you may require building regulations approval. An architect will understand all the relevant British Standards and can also prepare the relevant technical drawings. As part of their service, they will also manage the entire process on your behalf.

Builder Recommendations: We know that finding a good and reliable builder can be challenging. A local architect will work with lots of good builders who they have successfully worked with in the past.

A picture of a modern detached garage conversion
Create a fantastic new area to relax by converting your detached garage into a TV room

9. How do I find and hire someone to convert my garage?

Friends and Family: This is always the first place we would start. If anyone you know has recently had work carried out by a builder, their feedback is invaluable. It can also be a good idea to have a walk up and down your street to see if any neighbours have had extensions built recently. If they have, you can knock on the door and ask how their experience was over a coffee.

Builder website: There are so many fantastic websites to help choose the right builder for you. The advantage of these sites is that previous clients can leave reviews to give you the peace of mind that your builder will carry out a fantastic job. The two we would recommend are my builder and trusted trader.

Architect: An architect is also a great option if you’re looking to convert your garage. To find one, we would suggest taking to Google and having a read through their reviews. A second option is to go directly to the Architects Registration Board website (although they don’t include reviews).

10. Do I need Building Regulations approval for my garage conversion?

Garage conversions will usually require building regulations approval, as you are creating a habitable room. These have different requirements compared to a garage used to store a car.

Before starting works, we would always advise that you speak to a competent professional for advice. This could either be an architect, builder, or even your local authority building control department.

Here are a few factors which might affect building regulation approval.

Foundations: Often existing garages are relatively lightweight. This means the existing foundations may not be sufficient to accommodate the weight of a new floor, walls or roof, and might need to be upgraded.

Structural Strength: Many existing garages have walls made up of only a single layer of bricks. This may not be strong enough to carry the weight of a new floor or roof and may therefore need a second course of bricks.

Insulation: As people will be living in the new garage conversion, the new space will need to be insulated and weatherproofed.

Windows and Ventilation: All new windows will need to meet the energy efficiency standards and also provide ventilation.


Although garage conversions are relatively straightforward, there are quite a few steps to go through.

At Adara, our team of planners and architects have a huge amount of experience when it comes to garage conversions. We’re also very creative so can suggest some innovative ideas you might not have considered.

Feel free to call a member of our team for a free 30 min consultation anytime….we would love to hear about your ideas.

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