How To Install Underfloor Heating
The steps for laying wet pipes or electric mats under a new floor and where a professional needs to take over.
The short answer
To install underfloor heating, clear and level the subfloor, lay insulation, then fit the heating pipes or electric mats to the manufacturer's layout. Wet systems are connected to a manifold, pressure tested and covered with screed. Electric mats are resistance tested before and after laying, covered with tile adhesive or levelling compound, and wired in by an electrician.
Underfloor heating spreads gentle warmth across the whole floor rather than pumping heat out from one spot on the wall, and it frees up the wall space radiators take up. It can go under most floors, and there are two types to choose between. A wet system runs warm water from your boiler through pipes, while an electric system uses heating cables or mats.
Which one suits you depends on the size of the room, whether the floor is coming up anyway and how much of the job you want to do yourself.
Electric Underfloor Heating
Electric systems are the cheaper and simpler of the two to fit. The cables or mats roll out to the shape of the room and need far less floor build-up than pipes, which makes them a natural fit for bathrooms, en suites and kitchens where you're tiling anyway.
The trade-off is running cost. Electricity costs more per unit than gas, so heating a large area this way is dearer to run than a wet system or radiators. Several of the electric underfloor heating kits we recommend come with the mat, thermostat, floor sensor and fixings in one box, which makes them a realistic DIY project up to the point of wiring in.
Wet Underfloor Heating
A wet system is more involved to install but much cheaper to run. Pipes carry water from your boiler or heat pump to a manifold, which splits it into loops for each zone and lets you control the temperature room by room, just as you would with radiators.
Because it's plumbed into your heating system and buried in the floor, mistakes are expensive to put right. We'd have a heating engineer fit a wet system, or at the very least connect and commission it.
| Point to Compare | Electric | Wet |
|---|---|---|
| Installation | Simpler and quicker | More complex with a manifold and pipework |
| Running cost | Higher | Lower |
| Floor build-up | Very low | Deeper, with insulation and screed |
| Best for | Single rooms such as bathrooms | Large areas, extensions and whole floors |
| Who connects it | An electrician | A heating engineer |
How To Install Underfloor Heating Step By Step
The method depends on which system you're fitting, so we've split the steps in two. These are an outline of what's involved, and the instructions with your system always take priority.
Installing Wet Underfloor Heating
- Clear the subfloor and remove anything sharp or uneven that could damage the pipes, then sweep and vacuum it clean.
- Lay a damp-proof membrane on a solid floor, then fit rigid insulation boards and an edge strip around the walls to allow for expansion. Our guide to insulating floors properly covers the options.
- Fix the manifold to a wall in a spot where it can be reached later, close to where the flow and return from the boiler run.
- Lay the pipe in the clips or castellated panels to the manufacturer's layout, running each loop out from the manifold and back again without joints under the floor.
- Pressure test every loop and leave it under pressure while the floor is finished, so any damage shows up straight away.
- Cover the pipes with screed at the depth the system specifies, or fit spreader plates under a timber floor.
- Let the screed cure fully, then commission the system and bring the temperature up gradually before laying the final floor covering.
Installing Electric Underfloor Heating
- Make sure the subfloor is clean, dry, level and free of sharp edges.
- Lay insulation boards to stop heat escaping downwards, which also helps the floor warm up faster.
- Use a multimeter to test the resistance of the mat or cable before laying it, and note the reading against the figure on the label.
- Roll out the mat to the plan, turning it at the walls by cutting the mesh only. Never cut the heating cable itself, and keep it clear of where fixed units such as a vanity or bath will stand.
- Fit the floor sensor between two runs of cable and test the resistance again.
- Cover the mat with flexible tile adhesive or a layer of levelling compound, and test once more before the floor finish goes down. Our guide to using self-levelling compound shows how to get it flat.
- Have an electrician connect the thermostat and supply. In bathrooms, the wiring is notifiable building work and must be signed off.
What Affects The Cost Of Underfloor Heating
There's no single price for underfloor heating, because the cost is driven by a handful of things that vary from house to house. The size of the area is the biggest, followed by the type of system.
- System type: electric kits cost less to buy and fit, while wet systems cost more up front but less to run
- Existing floor: lifting tiles or a concrete floor adds labour and waste compared with a room that's already stripped back
- Floor build-up: wet systems need insulation and screed, which can mean raising floor levels or trimming doors
- Connection: a heating engineer or electrician is needed for the final connection on either system
Get at least two quotes for a wet system and ask what's included, especially the manifold, screed and commissioning.
Choosing An Underfloor Heating Thermostat
The thermostat is the part you'll use every day, so pick one that fits how you run the rest of your heating. A wet system can be controlled in the same way as your radiators, so it works with many smart thermostats for UK homes through a separate receiver or zone. Our explainer on how a smart thermostat connects to the boiler shows that setup.
Electric systems need a thermostat rated for the load of the mat, with a floor sensor so the floor never gets too hot. Most kits include one, and some are smart models with their own app.
Getting The Floor Right First
Underfloor heating suits most floor coverings, from tiles and stone to engineered wood and luxury vinyl such as Karndean flooring. Check that your chosen floor is rated for underfloor heating before you buy it.
The prep matters more than anything else. Once the heating is buried, any fault means lifting the floor to reach it, so take the time to level, insulate and test at every stage.
What People Also Ask Us
Can you install underfloor heating yourself?
You can install electric underfloor heating yourself up to the point of wiring it in, as most kits come with everything needed and clear instructions. An electrician must connect the thermostat and power supply, and in bathrooms the work has to be signed off. Wet systems are best left to a heating engineer because they connect to your boiler.
Do you need insulation under underfloor heating?
Yes, insulation under underfloor heating stops the heat disappearing down into the subfloor. Without it, the system takes longer to warm up and costs more to run, especially over a concrete slab. Rigid insulation boards go down before the pipes or mats, with an edge strip around the walls to allow the screed to expand.
Can underfloor heating go under laminate or wood flooring?
Underfloor heating can go under laminate, engineered wood and most luxury vinyl, as long as the flooring is rated for it. Check the manufacturer's maximum surface temperature and use the recommended underlay. Solid wood is the least suitable, as it can shrink and gap with the heat, while tiles and stone conduct heat best.
Is underfloor heating cheaper to run than radiators?
Wet underfloor heating is cheaper to run than radiators in most homes, because it heats a large surface at a lower water temperature, which suits condensing boilers and heat pumps. Electric underfloor heating is dearer to run than gas radiators because of the higher cost of electricity, so it's best kept to smaller rooms.
Is electric or wet underfloor heating better for a bathroom?
Electric is the better fit for a bathroom. A mat adds very little height, so it slips under the new tiles without raising the floor, and keeping it to one small room holds the higher running cost in check. Wet systems come into their own across large areas, extensions and whole floors. Bear in mind that wiring a mat in a bathroom is notifiable building work.
Why does the guide say to test an electric mat so many times?
Each test catches damage while it's still easy to fix. You check the resistance before laying the mat and note it against the label, again once the floor sensor is in, and a final time after the adhesive or levelling compound covers it. A reading that's changed tells you the cable's been damaged before the tiles go down, because once the heating is buried, any fault means lifting the floor.
Can I cut an electric heating mat to go round a bath or vanity?
You can cut the mesh but never the heating cable itself. Snipping the mesh is how you turn the mat at walls and work round obstacles, and the layout plan that comes with the mat shows where to do it. Keep the cable out from under the bath and vanity altogether, as there's no point heating the floor beneath them.
Do I need to pressure test the pipes of a wet underfloor system before screeding?
Yes. Test every loop before any screed goes on and keep it under pressure while the floor is finished, so a nicked pipe shows up straight away instead of after the screed has set. Running each loop out from the manifold and back in one length, with no joints under the floor, takes away the likeliest place for a leak.
Richard has spent years renovating properties and turning them into rentals and Airbnbs. Like a lot of people he started out as a beginner, and these days there isn't much DIY he won't take on.