Underfloor Heating in London Homes: Maintenance, Problems and Servicing
Underfloor heating is increasingly popular in London new builds and basement conversions. Understanding how to maintain it prevents costly failures and keeps it running efficiently.
Wet vs Electric Underfloor Heating
There are two types of underfloor heating:
- Wet (hydronic) UFH: water heated by the boiler (or heat pump) circulates through pipes embedded in the floor. Requires a manifold to distribute water across zones. More efficient for whole-house use.
- Electric UFH: heating mats or cables are embedded in the floor screed. Simpler to install in renovations. Running costs are higher. Suited to single rooms like bathrooms.
Annual Servicing for Wet UFH
Wet underfloor heating systems should be serviced annually, ideally as part of the boiler service. The engineer should:
- Check the manifold for leaks and correct zone valve operation
- Test flow rates through each circuit
- Verify inhibitor concentration in the system
- Check the system pressure
- Test the room thermostat and programmers for each zone
Common Problems
Uneven Heating / Cold Zones
If one or more zones are not heating adequately, the problem is usually at the manifold — a stuck zone valve, a flow-rate imbalance, or a thermostat not calling for heat. Balancing the manifold involves adjusting the flow rates on each circuit so they are equal — this requires a flow meter and is a job for a heating engineer.
System Sludge
The narrow pipes in a UFH circuit (typically 16–20mm) are more susceptible to blockage from system sludge than standard 22mm central heating pipework. Inhibitor maintenance and magnetic filtration are important.
Screed Cracks and Leaks
UFH pipes embedded in a sand/cement screed can occasionally develop leaks at joints — often caused by ground movement or poor original installation. Detecting a leak requires thermal imaging or electronic leak detection. Repair involves breaking out the screed above the leak, which is invasive and expensive.
Electric UFH: Common Problems
Electric UFH mats can develop faults from mechanical damage during or after installation, or from screed that is laid too hot. Testing with an ohmmeter before screed is poured during installation is critical. After installation, faults in the mat usually require complete removal of the floor covering and screed — avoid at all costs during fitting.
Frequently asked questions
How long does wet underfloor heating take to heat a room?
Wet UFH has a slow thermal response compared to radiators — it typically takes 1–2 hours to bring a room to temperature from cold. This means it works best on a timed programme that pre-heats the space rather than being used reactively.
What temperature should wet UFH flow water be?
UFH typically operates at 35–45°C flow temperature, much lower than radiators (65–70°C). This lower temperature makes it particularly well matched to heat pumps, which operate most efficiently below 55°C.
Can I fit a smart thermostat on underfloor heating?
Yes — smart thermostats such as Hive, Nest or Drayton Wiser are compatible with UFH systems. For zoned UFH, zone controllers are required at each manifold or room. Wireless smart zone controls are available that avoid the need for rewiring.
Why is my underfloor heating making a clicking or ticking sound?
Clicking or ticking from UFH is normal — it is the thermal expansion and contraction of pipes and the screed as the system heats up and cools down. Persistent loud banging is less normal and could indicate air in the system or a pipe not properly clipped down.