Why consider a garage conversion?

If you need extra space in your home, you do have a number of options open to you. You could build outwards from your current property or you could add another floor to your home. If you have a garage, you could also convert that into extra living space.

However, there is another option that could be afforded to you if you do have a garage. Rather than build into it, you could build over it. This way, you would still have the space you need for your car, bikes, tools, etc. but you would have the luxury of that extra living space above it. What you do with that space is, of course, up to you. You might want a guest bedroom for visiting friends and family. You might want that extra space for your teenage children if they aren’t yet ready to fly the nest. Or you might want a home office, a living area for elderly relatives, extra space for socialising and entertaining, or anything else besides.

Any type of home extension is cheaper than moving to a new property, and it is a lot less stressful too. Building an extension over a garage is an excellent idea for some, so if you are able to consider this option at your property, then it might be worth your while looking into what is involved.

We are going to take a look at what is involved with the process here, and we are going to give you an idea of some of the costs that can be expected. Get in touch with us if you would like to know more after reading.

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What is an over garage conversion?

Simply put, an over garage conversion is an extension over your garage. It can increase the size of your living area, whether your garage is directly attached to your home or not. As we suggested previously, you would have the opportunity to use the extra area for whatever you wanted, although people typically extend over the garage to create extra bedroom and bathroom areas. The world is your proverbial oyster, however, so you can plan your new extension according to your dream home ideals.

Before work begins you might need to contact your local council for planning permission. This isn’t always the case, but you should still get in touch with them before work begins, as you don’t want to build over your garage, and later find out you are breaching local laws.

In some cases, you might have to demolish your existing garage. Some people think that an over garage conversion is a relatively easy process, and assume that it’s simply a case of removing the garage roof to build on top of it. While this might be possible in some circumstances, you should still adhere to the guidance given by the architect and building professionals you hire, as you need to make sure the foundations of your garage are stable. If you build on top of what already exists, the foundations of the garage might not hold up, so you would be putting yourself and your property at risk. An over garage conversion sometimes works best with a newly built garage, so it is vital that you consult the relevant professionals in advance, as they will advise you on the best course of action with your project.

Is your garage attached or detached?

Whether you’re building a garage from scratch or using an existing garage, this has to be taken into consideration. If you are building on top of a detached garage, you will need to have a staircase installed. There might also need to be an extra entry point, depending on what you are using your garage for. A detached garage is perfect in some ways, as it can become a private annexe for guests or older teens who want their privacy, but you do need to consider the practicality if you are intending to use your new extension for older relatives, as they might not be able to manage the staircase. In such an instance, it might be better to consider another type of extension.

If the garage is attached, the extra space you have will be easily accessible from your home. However, it’s important to consider the rooms adjoining the extension, as if the extra space is next to an existing bedroom, for example, you might not want people coming in and out of the extension through the bedroom area. This is another reason why you might still consider adding an extra staircase, as some privacy will still be afforded to you and the people using the extension. You should also consider windows when building on top of an attached garage. If the extension is going to block off windowed areas, you might want to redesign the affected area of your home.

Each of the things suggested here will have to be factored into the cost to extend over your garage. We will consider some of the other cost factors below.

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How much does it cost to build an extension over a garage?

Building over your garage is a great idea, but it’s not a cheap proposition.

If you are building over an existing garage, then you are going to see a reduction in the build cost.

To rebuild a basic garage, the cost breakdown will usually be as follows.

  • A new foundation, including trench digging and filling – £2,250
  • Ground floor construction – £2,700
  • External garage walls – £3,900
  • Guttering and drainage – £1,200
  • Electrical provision – £1000
  • Doors and windows – £3,000
  • Garage storage and security – £500

With the extension over the garage space, you will need to add to these figures. You will need to factor in the cost of new walls, doors, windows, and extra electrical work, for example. The figures above will give you a rough idea of some of the costs that might be involved.

You are then looking at new flooring and a roof for your extension. Builders will generally work at an average build price of between £1000 – £2000 per square metre of an extension. When it comes to the flooring of your extension, this might drop to around £1000 per square metre if they were building over your existing garage structure. You would need to work out the cost depending on the size of your floor area. If it was 27 square metres, you would be looking at between £27,000 – £35,000. You will need to add to these costs if building an additional floor and when considering the size and type of your roofing. You can also reduce some of these costs if your garage is of a smaller size.

Factors affecting the cost of building an over garage extension

To rebuild or not to rebuild

Creating an extension over your existing garage would allow for a significant reduction in the build cost. Without the costs attributed to a brand new garage, you would be paying for the costs associated with the flooring, roofing, plumbing, electrics, and any associated fixtures needed for the rooms you wanted in your extension. However, even though the existing structure might accommodate an extension, you would have to make compromises. Your plans might have to change because you would be working from an existing footprint, so it might be that you do decide to rebuild your garage after all, especially if you need something of a larger size to better suit your vision.

When considering your garage, you might be forced into knocking it down if the brickwork was single skinned, as this means you would have less stability to manage the weight of another level of accommodation. The garage might have to be rebuilt with double-skinned brickwork to provide the extra stability your extension would need. You might need to have extra work done on the foundation too, so this is another reason why you might need to start from scratch with a new garage structure.

Rebuilding the garage will allow you to have the extension you actually want, with very few compromises. So, while you will have to factor in the costs of new brickwork, reinforced foundations, and the other costs we listed previously, you will benefit in the long-term if you can have the extension of your dreams. You will also have the opportunity to create a double garage, as this will afford you more space for your extension. Many single garages can be built over, but with limited size, you would only have space for perhaps one or two small rooms. A double garage can increase your area space and give you room to be more creative with your plans.

Planning permission

Before work begins, you might also have to submit to the needs of your local authority. Especially when consider neighbouring properties, there may be rules associated with the size of an extension, which apply not only to an over the garage conversion but to any type of extension. You should contact your local authority ahead of time, as while there may be no restrictions on what you can do with your garage, you should still get the go-ahead before building work begins to avoid the potential for any costly do-overs should they later scupper your plans. In such an instance, you will need to pay planning permission fees.

Usually, if an extension falls within your permitted development rights, you might not need planning permission. However, because there are structural elements to consider when building over a garage, you will need Building Control Approval from a council building inspector, so there will be small fees attached. Contact your local council office to find out more.

Other price factors to consider

There are other factors that need to be attributed to the overall cost too.

A new pitched roof will cost you around £40 per square metre if converting from a flat square roof.

If you wanted cavity wall insulation, you would be looking at around £400.

There would be costs involved when installing new plumbing and electrical fixtures, and these would depend on the types and size of the rooms you would be adding to your extension.

There will be costs attributed to the steel beams you would need to support the extension. These cost between £800 on average, but it depends on the size needed.

If the garage was attached to your property, you would be looking at around £100 for a new door to provide an entry and exit point.

There will also be costs attributed to types of material you decide to use for your extension, as well as labour costs. A timber frame extension, for example, is a popular option for many due to the relatively low cost when compared to other types of extension. You are looking at around £120 per square foot. The relative simplicity of this type will also reflect in the costs you are paying for labour, but it’s worth researching local building firms to get a firm idea of what to expect.

Hiring the professionals

You are unlikely to be planning the extension alone, unless, of course, you had the experience and qualifications behind you. Assuming you don’t, you would need to hire the relevant people to help you make your extension dreams come true.

When in the planning stages of your over the garage extension, you should consult with a specialist designer or an architect. They will advise you on the feasibility of your extension plans and will give you advice on what style of extension to go for, and what materials you might need to use. On average, the cost to hire an architect or a specialist designer is around £200 per day, and as a week is usually enough time to come up with completed design and technical specifications, you might be looking at a maximum of £1000 in total.

If building your garage from scratch, you will need to hire somebody to work on your foundations. As concrete is usually the foundation of choice, you will need a concrete layer. They usually charge around £75 per day, and depending on their skills and experience, they should have completed work within 3 days, if not sooner.

Assuming your garage and extension will be made from brickwork, you will need a specialist bricklayer with the skills to manage an extension. Depending on the complexity of the work involved, they will usually charge between £75 to £150 per day. The size of your extension, and whether or not you will be building a garage from scratch, will determine how long they need to complete the project.

To lead your project, you might want to hire a general builder. They will be responsible for hiring bricklayers and other labourers and will oversee some of the work that takes place. The cost of hiring a general builder is usually around £100-£150 per day.

At the end of the build process, you will need to hire an electrician to ensure your over the garage extension has an electrical supply. From lighting to socket fixtures, there will be much that needs to be done to ensure everything is in place. Most electricians charge around £125 per day for their services.

If you’re planning to have a kitchen or bathroom within your extension, you will require the services of a plumber. You are looking at around £300 per day for their services, although this will depend on the area you live in, as you might be able to hire somebody for less.

With regards to all labour costs, timescale is an important factor. The sooner a job is completed, the lower your overall costs will be. Of course, this doesn’t mean you should settle for any rushed jobs but assuming you hire the people with the necessary level of skill and experience, you won’t have to suffer costly mistakes and delays. We provide quotes from reputable companies, so when using our services, you can trust us to source quotes from those tradespeople who will provide the quality work you need for your project.

The timescale will also depend on the complexity of your project and the size of your build. It will also depend on whether you need to build a garage from scratch with your project. Take these factors into consideration when budgeting for your over the garage extension.

If you are building over an existing garage, then you are going to see a reduction in the build cost.

Frequently Asked Questions

These are some of the questions our customers often ask.

Is it possible to extend over a garage?

Yes, as we have already discussed, it is possible to extend over a garage. However, depending on the structural foundations of the garage, it might be that a new garage needs to be built if the foundations are weak. If the garage is single-skinned, it might be that it needs to be demolished and built with double-skinned brickwork to support the weight of the extension.

Why would you want to extend over your garage?

There are all kinds of reasons as to why you might want to extend over your garage. If your garage was attached to your house, you could benefit from an extra bathroom, for example. An attached or detached garage would also allow for extra bedrooms, added living spaces, hobby rooms, and home office areas. You might want to extend over your garage if extending into your garage wasn’t practical, perhaps because you still needed to have a space for your car and other household storage. And if it wasn’t possible to extend your home outwards, perhaps because of the size of your land, you might decide that an extension over your garage is the logical choice.

 How much does an over garage extension cost?

Building work will range from £1000 – £2000 per square metre of the extension, including the cost of the roof and the foundations. The price will depend on whether or not the build is taking place over an existing garage, the size of the garage, and the type of materials that are needed within the extension. Then there are all of those other costs that need to be factored in, including electrical, labour, and planning permission costs, so it’s important to use the price guide we offered, and to do your own research to find out more about the costs in your local area. You will have to factor the various furnishings and fixtures you require too, so you might want to sacrifice in some areas when budgeting for the overall cost to extend over your garage.

Do I need planning permission?

It depends on the size of your extension, and on how strong your foundations are. As discussed earlier, structural elements will need Building Control Approval. The materials you use should also be similar to those used on the outside of your home, so if you were planning on making any major external changes, you would need to seek planning permission. If you were to extend the footprint of the garage, you might also need planning permission, as there are laws and regulations concerning property boundaries.

How do I check whether the foundations are strong enough?

When building over an existing structure, you do need to ensure your foundations are adequate. You can do this by digging a test hole to expose your existing foundations and then inviting a Building Control Officer to inspect and assess your foundations to make sure they are suitable for the additional load of your planned extension. You should dig to a minimum of one metre, although you are, of course, entitled to hire somebody else to dig for you if you needed the extra assistance.

When building a garage from scratch, you can hire the relevant people to strengthen your foundations in support of your over garage extension project. If you wanted to keep your garage, but your foundations weren’t strong enough, you might want to consider underpinning. This is where a building firm will dig along the garage foundation to include additional footing and reinforcements. A structural engineer will need to be called in to assess the work done and to make sure everything is safe. This process can be expensive so a new garage build might be the safest way forward.

Will this add extra value to my home?

Yes, any extension will add value to your home, provided it has been completed satisfactorily. Adding space above your garage can increase the value of your property by 20%, as it automatically increases the ground area of your living space. A property is often valued according to the number of bedrooms it contains, so if you increased the count from three to four, you would increase the value of your home considerably. If your over garage extension also included an ensuite bathroom or another living area entirely, you would also see a jump in value. For more advice with regards your particular property, you should speak to an estate agent, as they would be able to give you further information on how much your house would be worth if you did extend it in this way.

If you decided against building over your garage, you could also increase the value of your property by building into your garage. Especially if your garage was used for a bedroom or a bathroom area, you would see a significant jump in value. There are other alternatives. You might consider a loft or a basement conversion, or you might want to build outwards on your current property. These are all good ideas, but the advantage of an over garage extension is that you don’t need to push closer towards your property boundaries, so there will be less infringement on your neighbour’s property area.

What are the benefits of building an extension?

Well, other than the fact that you would have greater functionality and added value to your property, you would also have less reason to move home if you wanted to stay put for the long-term. Rather than searching for your dream home, you could transform your current property into the home of your dreams. This can happen if you build over your garage, and it can also happen if you extend in any other way, perhaps by adding a sunroom to your property.

Why should I get extension quotes from Extension Prices?

It’s very important that you find contractors who will complete work to the highest of standards. We only use reputable and honest tradespeople so you can have the peace of mind that comes from knowing your extension is in the safest of hands. There will be less stress for you too, as you won’t have to manually receive quotes from the tradespeople in your area, as we will do all of the hard work for you. By using our services, you will be able to choose from the best quotes possible from the best people in your locale.

Rich Crossley
Having spent 30 years working all over the world for top-tier investment banks, I’ve owned and developed houses all over the world – Europe, the US and Asia. I’m now based back in the UK and involved in the property industry – oh, and I’m a keen DIY enthusiast!
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