Most converted garages are heated by extending the existing central heating with a new radiator, provided the boiler has enough capacity, or by electric heating or underfloor heating. Any shower room, WC, kitchen sink or washing machine needs a new waste route to the drains, which falls under Part H of the Building Regulations. Gas work must be carried out by a Gas Safe registered engineer, and the plumbing and heating design is shown on the drawings before work starts.
How will the converted garage be heated?
| Option | How it works | Good for | Things to check |
|---|---|---|---|
| Radiator on the existing system | Flow and return pipes extended from the nearest radiator or pipework | Bedrooms, offices, living rooms next to the house | Boiler capacity, pipe route through the wall, system balancing |
| Wet underfloor heating | Pipes laid in the new floor build-up, fed from the heating system | Rooms where wall space matters, open-plan kitchens | Floor height, controls, boiler or heat source suitability |
| Electric underfloor heating | Heating mats or cables under the floor finish | Shower rooms, small rooms, warming tiled floors | Running costs, separate circuit from a registered electrician |
| Electric panel heaters | Wall-mounted heaters on their own controls | Detached garages and annexes far from the boiler | Running costs, controls, circuit capacity |
There is no single right answer. The heating that suits a bedroom next to the hall will be different from what suits a gym at the bottom of the garden. Whatever is chosen, heating only works well when the walls, floor and roof are properly insulated first, which is why we plan heating alongside floor insulation and levelling and the rest of the fabric work. It is all part of planning a garage conversion for a Liverpool home as one job rather than a collection of trades.
Can my boiler cope with another radiator?
Often it can, but not always. A Gas Safe registered engineer or heating engineer looks at the boiler’s output, the number of radiators already on the system, the pipe sizes and how the system is controlled. Combination boilers, older systems and houses already at the limit of their heating may struggle with an extra room, in which case electric heating or a heating upgrade may be suggested. The new radiator also needs a thermostatic valve and the system needs balancing so the far end of the house still heats properly.
In an integral garage, the boiler is sometimes in the garage itself. It may be able to stay in place within a cupboard, or it may need relocating. Flues, ventilation and clearances are set by the boiler’s instructions and the gas regulations, so any change to a boiler or its flue is work for a Gas Safe registered engineer only.
Adding a shower room, WC, kitchen or utility
Water is easy to bring in; waste is the harder part. Every new sink, shower, WC and washing machine needs a waste pipe with enough fall to reach the drains, and the route usually runs under the new floor or through the wall to an existing drain run outside. The new floor build-up in a garage helps, because it gives some height to run pipes, but long runs and low drains can make gravity drainage awkward.
- Shower room or WCNeeds a soil pipe connection for the WC, a shower waste with enough fall, and extract ventilation. See our garage shower room page.
- Utility roomNeeds supplies and a waste for a washing machine and sink, plus space for a dryer and ventilation. See garage to utility room.
- KitchenNeeds a sink waste, dishwasher and washing machine connections, and sometimes a gas supply for a hob. See garage kitchen extensions.
- AnnexeMay need all of the above, plus hot water capacity for a second bathroom and a supply run across the garden.
Where gravity drainage really is not possible, a pump-assisted macerator is sometimes used for a WC or shower. They have their place, but they need power, maintenance and approval, so check with building control before relying on one. Any new drainage, including connections to existing drains, is checked by building control under Part H and is usually tested before it is covered.
What do the qualified trades do?
- Survey. The heating and plumbing engineer checks the boiler, water pressure, existing pipe runs and where the drains are.
- Design. Radiator sizes, underfloor heating layouts and waste routes are agreed and shown on the drawings.
- First fix. Pipes are run in the floor build-up and walls before insulation, screed and plasterboard close them in. Drainage is laid and tested.
- Inspection. Building control usually sees new drainage before it is buried or boxed in.
- Second fix. Radiators, sanitaryware, taps and appliances are connected once the room is plastered and decorated.
- Commissioning. The system is filled, bled, balanced and tested. Gas work is recorded by the Gas Safe registered engineer.
Plumbing and heating in detached garages
A detached garage is separate from the house’s heating and drains, so new pipes and cables have to cross the garden. Running heating pipes that far is possible but needs well-insulated pipework and a boiler with capacity, so electric heating is often more practical for a single room. Water supply and drainage routes are planned together with the electrical supply so the garden is only dug once. Larger plots in Heswall and Southport sometimes have detached or double garages big enough for an annexe, where this planning matters most.
Problems we see with old conversions
- Rooms heated only by a plug-in heater because the radiator was never connected.
- Radiators that barely get warm because the system was never balanced.
- Shower wastes with too little fall, causing slow drainage and smells.
- Unapproved drain connections found when a house is sold.
- Pipes laid in an uninsulated slab, losing heat into the ground.
Our garage conversion problems guide explains more of the issues buyers and owners run into.
Never carry out gas work yourself. Any work on a gas boiler, gas supply, hob or flue must be done by a Gas Safe registered engineer. If you smell gas, call the National Gas Emergency number on 0800 111 999.
Where we work
We plan plumbing and heating for conversions across Liverpool and Merseyside, from inter-war semis in Bebington to estate houses with integral garages in Widnes and Maghull. Whatever the house, a local garage conversion specialist can help you decide on heating and services early and keep the whole conversion on track.
Need heating or a shower room in your converted garage?
Call 07777 659786 or leave your details. Tell us what the room is for and where your boiler and drains are, and we will call you back to talk it through.
Frequently asked questions
Can I add a radiator to my garage conversion from the existing boiler?
Usually, if the boiler has enough capacity and a sensible pipe route exists. A heating engineer checks the boiler output, the existing radiators and the pipework. If the system is already at its limit, electric heating or a heating upgrade may be a better option.
Is underfloor heating a good idea in a converted garage?
It can be, because the floor is being rebuilt anyway with a membrane, insulation and screed. Wet underfloor heating runs from the heating system; electric mats suit smaller rooms such as shower rooms. Floor height, controls and running costs are the main things to weigh up.
Can I put a toilet or shower in my garage conversion?
Often, yes, if a waste route with enough fall to the drains can be found. New drainage falls under Part H of the Building Regulations and is checked by building control. Where gravity drainage is not possible, a macerator is sometimes used, but check with building control first.
Does a garage conversion need Building Regulations approval for drainage?
Yes. Any new drainage or connection to existing drains is covered by Part H, and building control usually wants to see it before it is buried or boxed in. The drainage route is shown on the drawings for the Building Regulations application.
My boiler is in the garage. Can it stay there?
It can often stay in place within a cupboard in the new room, as long as clearances, ventilation and flue requirements are met. If it needs moving, that work must be done by a Gas Safe registered engineer. This is checked at the first visit because it affects the layout.
How do you heat a detached garage conversion?
Electric panel heaters or electric underfloor heating are common because they avoid long heating pipe runs across the garden. Extending the central heating is possible with insulated pipework if the boiler has capacity. Good insulation of the walls, floor and roof matters most.