Underfloor heating not working
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →Underfloor heating is wonderfully efficient when it's working, but when a zone goes cold, it can be frustrating and confusing. The good news is that most faults are straightforward to diagnose without calling an engineer immediately. Wet underfloor heating systems rely on a combination of controls, actuators, water pressure, and pump circulation — and often the problem is something simple like a closed valve or a failed motor rather than anything serious. This guide walks you through the logical checks a professional heating engineer would perform, starting with the thermostat and working through to the manifold and boiler. If you're handy with basic checks and feel confident poking around your heating system, you can often spot the culprit yourself; however, if you need to adjust balancing valves or suspect a deeper fault, it's worth calling a Gas Safe registered engineer rather than risking damage to an expensive system.
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Most likely cause & what to check
Check the thermostat or smart controller for the underfloor heating zone — confirm it is calling for heat and set above the current room temperature.
Find the underfloor heating manifold (usually in a cupboard or utility room) — it looks like a series of pipes with flow meters and valves. Check all zone valves are open (handle inline with the pipe = open).
Check the actuators (small cylindrical motors on top of each manifold valve) — they should feel warm to touch when the zone is calling for heat. A failed actuator can be replaced for £15–£30.
Check the system pressure on the manifold gauge — wet underfloor heating is part of the sealed heating system and requires 1–1.5 bar.
Check your boiler is firing and that the circulation pump is running (you should be able to feel vibration on the pump body).
If individual zones are not heating but others are, and actuators are working, the manifold balancing valves may need adjustment. This is a job for a heating engineer.
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Frequently asked questions
Why has my underfloor heating suddenly stopped working?
The most common causes are a failed actuator (the small motor on the manifold valve), a closed zone valve, low system pressure, or a boiler that's shut down. Start by checking your thermostat is calling for heat and above the current room temperature, then inspect the manifold to see if zone valves are open and actuators are warm.
Is underfloor heating expensive to repair?
Many repairs are affordable — a failed actuator costs £15–£30 to replace, and simply opening a closed valve is free. More complex work like balancing valves or pump faults will require an engineer and can cost £150–£400, but these are less common than simple control failures.
Can I fix my underfloor heating myself or do I need an engineer?
You can safely check thermostats, valve positions, actuator warmth, and system pressure yourself. However, adjusting balancing valves, diagnosing pump faults, or replacing components on a sealed system should be left to a qualified heating engineer to avoid voiding warranties or damaging the system.
What does the pressure gauge on my underfloor heating manifold mean?
Wet underfloor heating is part of a sealed system that requires 1–1.5 bar of water pressure to circulate properly. If the gauge reads below 1 bar, the system has lost pressure and will not heat; you'll need to repressurise using the fill loop, or call an engineer if you're unsure how to do this safely.
How do I know if the actuator on my underfloor heating manifold has failed?
When the thermostat calls for heat, a working actuator should feel noticeably warm to the touch within a minute or two. If it stays cold even when the zone is demanding heat, the actuator has likely failed and needs replacing — it's a simple swap that costs very little in parts.
Why is only one zone of my underfloor heating not working?
If other zones heat normally, the issue is isolated to that zone's valve, actuator, or controls. Check that zone's valve is fully open and the actuator warm; if both are fine, the problem may be a blocked pipe or a failed balancing valve, which requires an engineer's attention.