Planning a garage conversion
Converting your garage is one of the most cost-effective ways to add extra space without building a new extension as in many cases, you won’t need to dig new foundations. Plus, you don’t need to sacrifice any of your garden.
The structure of your existing garage will need to be assessed to get a better idea of its potential, the work required and costs involved. It’s always a good idea to get expert advice from a building professional, such as an architect or structural engineer. If the foundations need to be reinforced, the ceiling heights raised or the walls, floors or roof replaced, it will add thousands of pounds to your project. In addition, you may need an extra staircase if you extend above the garage. This will involve looking at possible access from the main house.
Remember in many cases, a garage is little more than a thin-walled shed – perfect for storing a car. Turning it into a comfortable living space means upgrading the floor, roof and walls. In some cases, it may be cheaper to knock the garage down and start again.
Design ideas
Single garages are often long, narrow spaces with low ceilings. So how can you transform it into bright, light-filled room? If the garage faces the garden, replacing one wall with floor-to ceiling windows or bifold doors will make it feel more spacious and improve the connection with outside. If the garage already has small windows, consider installing bigger picture ones and rooflights to bring in even more light.
A key part of a garage conversion is infilling the old garage door opening with a new brick wall and possibly a window and new door. A structural engineer will need to assess if the garage foundations were continued beneath the opening and are adequate to support the new wall or need strengthening. This may involve digging a small trial hole to check.
Make sure the brickwork, materials and windows replacing the garage door blend in with the existing house. If you can’t match the building materials, you can opt for a new contrasting style, such as oak cladding.
Electrics and plumbing
Ask a suitably qualified electrician to assess the wiring and electrics in your existing garage. Hopefully, it will all be up to date but if not, rewiring the garage for lighting and other electrical uses may require the installation of a new consumer unit or fuse box which will bump up costs. The building control department of your local planning authority will need to confirm whether your converted garage is safe to live in and sign everything off, including the electrics. All electrical installations must comply with British Safety Standards.
If your electricity meter or boiler is in the garage it can be costly to relocate elsewhere. A cheaper option is to box them in with wooden units, painted to match your new décor. If it’s too much hassle to lay new pipework, think about electric wall heaters or electric underfloor heating.
Will you need plumbing for a sink, shower or washing machine? A plumber will need to create a system for the water to flow in and out with two separate sets of pipes. A toilet will need a soil drain.
Insulation
Garages are often built with a brick or block single skin solid wall without any insulation at all. A key part of the building work will be adding insulation. Building Regulations require the floor, roof and walls to be insulated to a certain U-value or rate of heat loss through that element.
For the walls, the simplest approach is often to use insulated plaster board (protected by a damp proof course) fixed between timber battens and wall. Insulation for the roof will vary depending on whether its pitched or flat – and whether you want to build above it. If the garage has a solid concrete floor, builders could lay polystyrene boards on top of the existing slab with a new layer of screed along with your new floor covering. It’s at this point you need to think about underfloor heating.
Garage ceilings are often lower than in the main house and so adding floor insulation could further reduce head room. However, floor insulation should be part of the conversion if possible.
Do I need planning permission?
Planning rules are another factor to consider. The good news is that in May 2019, planning rules were slightly relaxed. If the building work is internal only the project can usually be completed under permitted development rights. But if you are replacing the existing garage door with a new brick wall and/or adding windows to the front, side or rear, it is highly likely planning permission will be required. Issues such as overlooking your neighbours may need to be considered.
The rules can be complex, so seek guidance from your local planning authority or an experienced local architect. Check your property deeds to see if there were any planning conditions attached to the house when it was built, such as the garage must remain for parking which will need to be lifted before work starts.
If your garage conversion is allowed under permitted development, it is a good idea to apply for a Certificate of Lawful Development (add link), especially if you aim to sell in future. If you live in a Conservation Area or National Park or your home is listed, the rules are different and planning permission is needed.
And Building Regulations?
Converting a garage into liveable space will always require Building Regulations approval, so your local council needs to be informed. This involves submitting a building notice or full plans application to the building control department of your local planning authority. This is your legal responsibility as homeowner although your building professional may do this on your behalf. A building control officer will then visit to inspect the project at various stages and issue a final certificate on completion if it ticks all the boxes. You can use the council’s building control service or an approved independent inspector.
To comply with building regulations, your garage conversion must be:
Structurally sound. For example, the foundations, walls and roof will need to be assessed and reinforced if required
Have safe electrics. Certain electrical work must only be carried out by a suitably qualified electrician and all new and existing electrics will need to be safety-tested
Energy efficient with floor, wall and roof insulation
Have a damp proof course and good ventilation
Have fire escape routes and fireproofing
Do I need an architect and other expert help?
Most good builders should be able to plan and carry out a straightforward garage conversion. That said, you may choose to hire an architect or architectural technologist depending on the size and complexity of your project. A structural engineer will definitely need to be involved to satisfy your local planning department that your conversion is structurally sound. The engineer will provide plans and calculations.
Architects, architectural technologists and surveyors can all ensure building regulations have been complied with and provide advice and support throughout the project. They will also have experience of liaising with building control inspectors.
Alternatively, if you only have a small budget and are a skilled DIY-er, another option is to plan and build the garage conversion yourself. Just be aware that your work will be checked by a building control inspector and any work that doesn’t comply with building regulations will have to be redone at your expense. For anyone intending to go down the DIY route, the advice is to leave any specialist work to the experts, including electrical, structural and complicated plumbing.
