There are many reasons a garage conversion is a home improvement project well worth considering. If you have an attached garage that is doing nothing but gathering clutter and a need for extra space, then converting the garage into living space is a great idea, and much more cost effective than building an extension.
A garage conversion is also a project that creates minimum disruption to your living conditions whilst work is underway.
Costs start at around £8,000 for a basic garage conversion, but it is a good idea to carry out a garage conversion in tandem with a remodel of your existing ground floor. This will allow you to rethink your whole floorplan, ensuring you really maximise both space as well as the way natural light will flow throughout the new space.
This guide explains everything you need to know about converting your garage into habitable space.
(MORE: Garage Conversion Ideas)
Do I Need Planning Permission for a Garage Conversion?
The short answer is: probably not.
Most integral garage conversions do typically fall under Permitted Development, meaning planning permission is not required. However, it is still best to check with your local authority.
If you live in a conservation area or in a listed building, you will almost certainly need planning permission. It is also worth checking for any planning conditions attached to the house or garage when constructed (i.e, the garage has to remain as parking) before beginning works as an application will need to be submitted to remove the conditions.
(MORE: What are Planning Conditions?)
If the conversion falls under Permitted Development, applying for a Lawful Development Certificate (LDC) is a good idea, particularly if you aim to remortgage or sell the house in the future.
If you are converting a separate, stand-alone garage as opposed to an integral one, then you may have to apply for a change of use.
How Much Does a Garage Conversion Cost?
A basic integrated garage conversion will cost from around £8,000 (or £400-640/m²). This is less than the value you could add to your home by converting the garage, so this is one project that really does make great financial sense.
Before you begin work, be sure to familiarise yourself with the factors that are likely to affect the cost of your garage conversion, including:
- the foundations need reinforcing
- the walls, floors or roof are in dubious condition
- the ceiling height needing to be raised (you need around 2.2-2.4m of headroom once the floor has been raised to 15cm above the external ground level)
- design fees
- planning applications
- the services of a structural engineer.
Do I Need an Architect for a Garage Conversion?
Whether you decide to use an architect, another house design professional or come up with designs yourself is a personal decision that should be based on the scale and complexity of the project.
Using an architect, an architectural technician or another type of design professional will mean expert design input and ideas that you might not have thought of. A design professional will also have useful trade contacts and will have experience in dealing with Building Control.
In terms of design fees, expect to pay from as little as £1,200 right up to £3,000, depending on the complexity of the design.
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 could also use a recommended builder — most good builders will be able to take on a garage conversion.
These companies will have plenty of experience in terms of dealing with any planning issues surrounding garage conversions, as well as building regulations.
Another option is to use a garage conversion specialist — these companies usually have a wealth of experience but, as with all of the above options, be sure to view completed projects and speak to past clients first.
Do Garage Conversions Need Building Regulations Approval?
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Yes, a garage conversion will need Building Regs approval.
You or your builder will need to adhere to the Building Regulations when converting an attached garage into habitable space. The Regs apply to various aspects of the construction, including:
- thermal performance
- fire safety
The LABC website is a really good starting point for information regarding the Regulations surrounding garage conversions in England and Wales.
A building notice or full plans application will need to be submitted to building control as part of this process. Your local building control department will then register the conversion and carry out inspections throughout the project, then issue the final certificate on completion.
Will Foundations Need Reinforcing for a Garage Conversion?
On of the key elements of converting a garage is blocking up the existing garage door opening (with an infill wall) — perhaps adding a new window or entry door in its place.
In order to add an infill wall, you’ll need to establish whether the garage foundations were continued beneath this opening and/or the concrete slab is adequate to support the new wall. This may involve digging a small trial hole in front of the concrete slab to check.
If the existing concrete slab is 200mm or over, this is generally adequate to extend straight up with new brickwork.
Speak with your designer, builder or a structural engineer in order to ascertain the suitability of your foundations.
There are two main routes for those who find their existing garage foundations are inadequate.
Either a 1m footing wall will have to be dug and filled with concrete, or a 140mm x 100mm concrete lintel can be added into the wall, below ground level, on both sides. You can then proceed to build a new infill wall on top.
How Should I Insulate my Garage Conversion?
If you want to use your garage conversion as a living space, you will need to ensure it is properly insulated.
Adding external insulation is not usually recommended as, although it minimises the impact that extra insulation will have on internal spaces, it can cause issues externally with wall thicknesses.
The simplest method is to use insulated plasterboard, fixed to timber battens that are protected by a strip of damp proof course (DPC) placed between batten and wall. Alternatively, insulation can be placed between battens, before a fireproof plasterboard is fixed to them.
In terms of roof insulation, you will only need to look at this if there is no room above the garage already.
- In pitched roofs, go for two layers of 150mm glass fibre quilt, one between the joists, another over as usual
- Flat roofs tend to need one layer between of rigid PUR insulation board and another below — the space in between flat roof joists however can’t be entirely filled. A 50mm air gap must be left above for ventilation. The second layer underneath will drop the ceiling height a bit. Typically 150mm deep flat roof joists will receive 100mm of PUR insulation between the joists and 50mm beneath them
Floor insulation is always absent in a garage and including some in the conversion should be part of the project, whenever it’s possible.
Garage floors are often lower than the house floor and so adding a damp proof membrane (DPM), insulation and a new screed, along with your final floor covering, is a good way to bring the levels up to that of the rest of your house.
You can use the existing concrete floor as a base, adding a solid or liquid DPM, before fitting a layer of insulation on top — building control will advise on how much insulation will be required.
Finally, the new screed is poured, ready to take your new floor covering. Be careful not to cover up any existing air bricks.
This is a good time to think about include underfloor heating within your garage conversion.
When working with very large differences in floor levels, a new suspended timber floor is a good idea. Aim to create a void beneath of at least 150mm between the concrete and underside of the timber, placing insulation between the joists, with new air vents to provide ventilation.
Plumbing and Electrics in a Garage Conversion
- Make a thorough survey of the plumbing and wiring in the house and garage. Any wall you plan to pierce for doorways or windows needs special attention
- Locate the main outflows for water, and, if you plan to install a toilet, the soil outflow
- Check the garage for wiring in the walls and ceiling. Rewiring the garage for lights and electric radiators will place additional strain on the household mains, which is fused at 100 amps
An additional mains supply can be installed, with the cost varying from £500 to £20,000. This will also require the installation of a separate consumer unit.
It is possible to locate the garage on the current consumer unit. If it doesn’t have its own miniature circuit breaker (MCB), consider replacing the consumer unit or upgrading it.
If the garage is to be another habitable room in your house, its own MCB is probably enough. Consider adding at least one new 20-amp circuit.
Wiring to a detached garage can be run through an underground conduit. If it is to be a separate dwelling, a new connection may be required, depending on likely power usage; consult an electrician.
What are the Fire Regulations for Garage Conversions?
You will need to consider fire safety and the regs when it comes to your garage conversion project.
“Attached garage conversions are usually accessed by a hallway door, providing a safe means of escape to outside, but if you can only enter this new room from another (outer) room, it defines it as an inner room,” explains building control officer Paul Hymers.
“Because a fire in the outer room could prevent your escape, the inner room will need an alternative escape route. That could be a door or window and so the role is often performed by the one replacing the garage doors at the front. Escape windows have minimum criteria. If you inner room is a kitchen, en suite, cloakroom WC or bathroom then it doesn’t need an alternative exit.”
In partial conversions, where only part of the garage is being used as habitable space, the wall separating the two should be fire-rated to 30 minutes.
Should I Convert my Garage?
Whilst a garage conversion is, in the majority of cases, a brilliant way to add space and value to your home, there are certain instances where it might not be a viable option or might cause more problems that it is worth. Consider whether this project is right for you by thinking about the following:
- Will the work mean one or more existing rooms will frequently be rendered unusable by building work?
- Remember that you will be held responsible for the legality of work done on your property. Time and energy will be required supervising work, being present to allow tradespeople access and making design and other decisions
- Will planning permission be granted? Is the house listed or in a designated area?
- Might the cost of reinforcing foundations, a new roof etc. mean you are paying more than you expected?
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