The essentials in 30 seconds
There are two kinds. Wet underfloor heating runs warm water from a boiler or heat pump through pipes under the floor; because the whole floor gives off heat, it works at lower flow temperatures than radiators, which the Energy Saving Trust says helps a boiler or heat pump run more efficiently. Electric (dry) systems use heating mats or cables and suit small areas warmed quickly, such as a bathroom floor. Whatever the type, the floor needs insulation beneath it, a finish that lets heat through (stone and ceramic tiles are best; carpet plus underlay at 2.5 tog or lower), and controls in each room. A wet system is designed and commissioned by a qualified installer; an electric one is connected by a qualified electrician.
- Wet systems fit best when you are laying a new floor: a new build, an extension or a full renovation.
- New or fully replaced wet systems in England should be designed for a flow temperature of 55°C or lower.
- Keep the pipe or cable layout drawings: you will need them before drilling or fixing anything into the floor.
How underfloor heating works
Underfloor heating warms the floor, and the floor then releases heat evenly across the room, giving a steady temperature from wall to wall. Because the heated surface is so large, it can run at a lower temperature than a radiator and still heat the room. The pipes or cables can be laid in different patterns to suit each room, closer together where more heat is needed.
Wet vs electric underfloor heating
| Wet (water-based) | Electric (dry) | |
|---|---|---|
| How it heats | Warm water from a boiler or heat pump flows through pipes under the floor | Electric mats or cables heat up when current runs through them |
| Best for | Whole floors and whole homes, especially with a heat pump | Small rooms and comfort underfoot, such as a bathroom or en-suite |
| Energy | Runs at low flow temperatures, which helps boiler and heat pump efficiency | Uses electricity directly, like a direct-acting electric heater |
| Floor build-up | Pipes usually in a screed or a panel system over insulation | Thin mats or cables, often in adhesive or a thin screed |
| Connection | Installer connects it to the boiler or heat pump through a manifold | Qualified electrician connects it to the supply |
| Controls | Room thermostats drive actuators on the manifold | Room thermostat with a manual override, often with a floor sensor |
The Energy Saving Trust describes electric systems as effective for quickly warming small areas, and less suited to heating large spaces for long periods, because they use electricity directly. Wet systems are the natural choice where underfloor heating will be the main heating for a floor or a whole home.
Screed depth for electric cables
Approved Document L for England sets limits for electric cables laid in screeds: direct electric cables within screeds no thicker than 60 mm, and night storage systems within screeds at least 65 mm thick, with fast-response heaters such as panel heaters covering at least 20% of the floor area. The 2026 edition adds that tile adhesive and levelling compound count as screed.
New build, renovation or retrofit
| Project | Usually suits | Points to plan |
|---|---|---|
| New build or extension | Wet, laid in the new floor with insulation beneath | Design it with the heat source from day one |
| Full renovation with a new floor | Wet, especially on the ground floor | The Energy Saving Trust notes you save effort when the floor is being replaced anyway |
| Ground floor only | Wet underfloor downstairs, radiators upstairs | Upstairs radiators often need to be larger to work at the same lower flow temperature |
| One bathroom or kitchen floor | Electric mats under tiles | Check the floor height at door thresholds and the electrical supply |
| Existing floor kept in place | Discuss low-profile options with an installer | Floor height, doors, skirting and stairs all change |
Floor build-up is the practical limit in many homes: insulation, the heating layer, any screed and the finish all add height at doors, skirting and stairs. Ask for a section drawing showing every layer and the finished floor level before you commit.
Insulation beneath underfloor heating
Heat travels both up and down. Without insulation underneath, much of it warms the ground or the ceiling below. Approved Document L (England, 2021 edition, in force until the 2026 edition takes effect on 24 March 2027) sets these minimums:
| Situation | Guidance |
|---|---|
| Ground floors and floors exposed to outside air | Insulate to limit downward heat loss to no more than 10 W/m² |
| Systems run intermittently, or laid over unheated rooms | A layer of insulation with a thermal resistance of at least 1.25 m²K/W between the heating and the structural floor |
| Intermediate floors, electric systems | Thermal resistance of at least 0.5 m²K/W (as in BS EN 1264-4) |
| Intermediate floors, wet systems | Thermal resistance of at least 0.75 m²K/W (as in BS EN 1264-4) |
| Pipework that heats no room | Insulated |
The 2026 edition keeps these figures, applies the 1.25 m²K/W layer to floors directly above the ground as well as unheated or intermittently heated spaces, and asks designers to account for the thermal resistance of the floor covering. Scotland, Wales and Northern Ireland have their own building regulations, so check with your local building control.
Underfloor heating with a heat pump
Heat pumps send water round the system at a lower temperature than a traditional gas or oil boiler. The Energy Saving Trust explains that underfloor heating, with its large surface area, can give out enough heat at that lower flow temperature, and that a lower flow temperature should help the heat pump run much more efficiently. If the underfloor heating is part of a heat pump installation, the installer designs both together.
- Design temperature: Approved Document L says new or fully replaced wet heating systems should be sized to heat the home at a maximum flow temperature of 55°C or lower, or the lowest workable temperature where that is not feasible. Underfloor heating is one of the easiest ways to meet it.
- Mixed systems: with underfloor heating downstairs and radiators upstairs, the radiators must be sized for the same low flow temperature, which usually means larger radiators with more panels.
- With a boiler: BEAMA's controls guide says a high-temperature boiler needs a blending valve so the floor receives water at its design temperature, typically 40°C to 55°C, plus a high-limit thermostat that stops water above 60°C entering the loops.
Floor coverings for underfloor heating and tog limits
Different finishes pass heat at different rates, which changes how quickly a room warms.
| Finish | How it works with underfloor heating | What to check |
|---|---|---|
| Stone and ceramic tiles | Transfer heat efficiently; the Energy Saving Trust calls them a good option | Adhesive suited to heated floors |
| Engineered wood | Its layered base helps it cope with the temperature changes | The manufacturer's approval and maximum surface temperature |
| Vinyl and laminate | Can be suitable | Thickness, and the maximum surface temperature; BEAMA gives about 27°C for high-vinyl coverings |
| Carpet | Works, but the room takes longer to warm | Total tog of carpet plus underlay, 2.5 or lower |
| Rugs | Slow the heat in the area they cover | Keep large, thick rugs to a minimum |
Where a covering has a maximum surface temperature, BEAMA recommends a floor surface limiting thermostat that measures the warmest part of the floor and switches the heating off in that area until it cools. Choose the finish before the system is designed: the installer needs it to calculate pipe spacing and output.
Underfloor heating controls
Approved Document L says every new underfloor heating system should have controls to adjust its operating temperature, with a manual override on room thermostats for electric systems and automatic setback at night or when rooms are unoccupied where the screed is more than 65 mm thick. BEAMA's guide for wet systems adds:
- A thermostat or sensor in each room. Two rooms with a similar use, such as a kitchen and utility room, may share one; bedrooms and en-suites each need their own.
- Time control for each zone of up to 150 m².
- Night setback on thick screeds that lets rooms cool by only about 3°C overnight, avoiding big temperature swings.
- A boiler interlock, so the heat source and pump switch off when no room is calling for heat.
- Balanced flow meters on the manifold, set to the litres per minute in the design for each circuit.
Underfloor heating maintenance
- Commissioning: the 2026 Approved Document L asks for all underfloor heating equipment to be commissioned to BS EN 1264-4. Ask for the commissioning sheet, the flow-meter settings and the layout drawings, and keep them with the house documents.
- Heat source: have the boiler serviced every year (see our boiler service guide) or the heat pump maintained as its installer advises.
- Air in the circuits: wet systems are bled at the manifold, circuit by circuit; see how to bleed a radiator for pressure checks.
- Manifold checks: look for drips at the manifold and actuators, and check that each flow meter still shows flow when its room calls for heat.
- Electric systems: test the floor sensor and thermostat at the start of each heating season, and call an electrician if a zone stays cold.
Underfloor heating pros and cons
| Pros | Cons |
|---|---|
| Even, consistent temperature across the room | Adds height to the floor and needs careful planning at doors and stairs |
| A warm, comfortable floor underfoot | Thick screeds and carpets make it slower to warm up |
| Frees wall space with no radiators to work around | Fitting is disruptive unless the floor is being replaced anyway |
| Furniture and curtains block less of the heat | Repairs under a finished floor mean lifting the finish |
| Wet systems pair well with heat pumps at low flow temperatures | Electric systems use electricity directly and suit small areas best |
Is underfloor heating worth it
Underfloor heating tends to make the most sense when:
- You are replacing the floor anyway, in a new build, an extension or a full renovation.
- You plan a heat pump, or want your boiler to run at lower flow temperatures.
- You have room for insulation beneath and can accept the extra floor height.
- You want comfort underfoot in a bathroom, where a small electric mat is a simple upgrade.
Get a heat loss calculation and a written design before you decide, and ask the installer how they meet Approved Document L.
Underfloor heating: frequently asked questions
Is wet or electric underfloor heating better?
Wet suits whole floors and pairs well with heat pumps and boilers at low flow temperatures. Electric suits small areas, such as a bathroom, warmed for short spells.
Is underfloor heating worth it?
It is most worthwhile when you are laying a new floor, planning a heat pump, and have space for insulation beneath.
Does underfloor heating work with a heat pump?
Yes. Its large surface area gives out enough heat at the low flow temperatures heat pumps work best at.
Can you put underfloor heating under carpet?
Yes, but the room warms more slowly. Keep the carpet and underlay to a combined 2.5 tog or lower.
What is the best flooring for underfloor heating?
Stone and ceramic tiles transfer heat best. Engineered wood, suitable vinyl and laminate also work within their temperature limits.
Do you need insulation under underfloor heating?
Yes. Approved Document L sets minimum insulation beneath it so the heat goes up into the room.
How hot does underfloor heating water get?
Design temperatures are low: BEAMA gives a typical 40°C to 55°C behind a boiler, with a high-limit thermostat stopping water above 60°C.
Does underfloor heating need a thermostat in every room?
Building guidance and BEAMA's controls guide call for room-by-room control, with only similar rooms such as a kitchen and utility sharing one.
Sources
UK energy guidance, building regulations and trade guidance, checked on 27 October 2026.
- Energy Saving Trust · Underfloor heating ↗Wet and electric systems, flow temperatures, heat pumps, floor finishes, the 2.5 tog figure for carpet and underlay, benefits and installation by qualified professionals.
- GOV.UK · Approved Document L, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments ↗The 55°C maximum flow temperature, underfloor heating controls, insulation resistances and screed depths for electric cables.
- GOV.UK · Approved Document L, Volume 1: Dwellings, 2026 edition ↗Takes effect on 24 March 2027; insulation over the ground, floor covering resistance, adhesive counted as screed and commissioning to BS EN 1264-4.
- BEAMA · Underfloor heating controls guide for domestic properties ↗Blending valves and design temperatures, the 60°C high limit, room thermostats, zoning, night setback, boiler interlock, flow meters and surface-limiting thermostats.
Planning underfloor heating?
Choose the floor finish, check the floor height you can spare and ask installers for a heat loss calculation and a layer-by-layer drawing.