Underfloor heating warms a room from the floor up, using either warm water pumped through pipes or electric mats laid beneath the floor surface. A wet system — the type this guide focuses on — circulates heated water through a network of pipes, turning the whole floor into a gentle, low-temperature radiator. It is most often run from the same boiler or heat pump that supplies the rest of the home.
What underfloor heating is and how it warms a room
The principle is simple. Pipes carrying warm water are spread across the floor area in loops, and the heat rises evenly through the room rather than radiating from one or two fixed points on a wall.
Because the heated surface is so large, the water inside the pipes does not need to be very hot. A wet system typically runs at around 35–50°C, well below the 60–75°C a radiator circuit might use. This lower temperature is part of what makes underfloor heating well suited to heat pumps, which work most efficiently at modest flow temperatures.
The warmth tends to feel more even underfoot, with fewer cold corners and no hot spots near a radiator. It also frees up wall space, since there are no panels to work around.
Wet systems versus radiators
Underfloor heating warms a room from the floor up, using either warm water pumped through pipes or electric mats laid beneath the floor surface.
Both deliver heat, but they do it differently. Radiators heat the air close to them quickly, then rely on that warm air circulating around the room. Underfloor heating warms a large, low-temperature surface, so the room heats more gradually and holds its temperature steadily.
The trade-offs are worth understanding before committing:
- Response time: radiators warm a cold room faster; an underfloor system takes longer to come up to temperature but also cools more slowly, so it suits steady, all-day heating rather than short bursts.
- Floor build-up: a wet underfloor system adds height to the floor, which matters in a retrofit where door clearances and step levels are fixed.
- Running temperature: the lower flow temperature can improve efficiency, especially with a heat pump.
- Disruption: fitting it usually means lifting or building up the floor, so it is far simpler in new builds or during a major renovation than as a standalone job.
Many homes use a mix — underfloor heating downstairs on a solid ground floor, and radiators upstairs where retrofitting pipework into existing timber floors is harder.
How a system is laid and screeded
The floor build-up matters as much as the pipes themselves. A typical installation starts with insulation laid over the structural floor, which stops heat escaping downwards and pushes it up into the room.
The pipe loops are then fixed on top of the insulation, usually clipped to the insulation board or held by a profiled panel that locks the pipe in place. The loops are spaced according to the heat the room needs — pipes closer together near large windows or external walls, for example.
Once the pipework is fixed and pressure-tested, it is covered with screed. Screed is a layer of sand-and-cement (or a flowing liquid mix) poured over the pipes to encase them and spread the heat evenly across the floor.
- Traditional sand-cement screed is laid thicker, typically 65–75mm, and needs a longer drying period — often several weeks before the heating can be commissioned gently.
- Liquid (flowing) screed self-levels, can be laid thinner, and tends to surround the pipes more completely, which can improve heat transfer.
In retrofits where added height is a problem, low-profile systems use slim panels that sit on the existing floor, sometimes with little or no wet screed. These reduce the build-up but can change how the system responds. Whichever approach is used, the screed should be allowed to cure properly, and the heating brought up to temperature slowly the first time to avoid cracking.
Manifolds, zones and controls
The manifold is the hub of a wet underfloor system. It is the point where the warm water from the boiler or heat pump is distributed into the separate pipe loops and collected again on the way back.
Each loop connects to the manifold, and flow meters on it let the loops be balanced so every part of the floor gets the right amount of warm water. A pump and a mixing valve are often built into or sit alongside the manifold, blending hot water down to the lower temperature the floor needs.
Control comes from zone thermostats. A zone is simply an area — a single room, or a group of rooms — controlled together. A zone thermostat measures the temperature in that area and opens or closes the relevant loops at the manifold through small electric actuators (valves) to hold the set temperature.
This lets different rooms run at different temperatures and on different schedules. A kitchen might be warm through the day while a spare bedroom stays cooler. Programmable or smart thermostats add timing and remote control, though the slower response of underfloor heating means it rewards steady scheduling more than frequent adjustment.
Is it worth it for your home?
It depends heavily on the floor and the project. The strongest case is a new build or an extension being built from scratch, or a renovation where the floor is already coming up — here the pipes and insulation can be designed in with little extra disruption.
A solid ground floor on a heat pump is a natural fit, because the low flow temperature plays to both technologies' strengths. Well-insulated rooms with large open areas and tiled or stone floors, which conduct heat well, also see the benefit clearly.
Retrofitting into an occupied home with timber floors is more involved and may mean accepting low-profile systems or partial coverage. It is also worth considering floor coverings: thick carpet with dense underlay insulates against the heat and reduces output, while tile, stone and engineered wood transmit it better.
Before deciding, it helps to weigh the heat demand of each room, the floor build-up the structure can take, and how the system will be controlled. A heating engineer can carry out a heat-loss calculation to confirm whether underfloor heating alone can meet a room's needs or whether it works best alongside other heat sources.