Start With What Your Floor Is Actually Doing
Almost every wet underfloor heating fault falls into one of four groups. Once you know which group your symptom belongs to, the list of likely causes gets very short. Pick the description below that sounds most like your system.
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Controls & Thermostats
The thermostat is blank, unresponsive, calling for heat with nothing happening, or the controls are too old to get parts for.
Controls faults & replacements → -
Cold Spots & Flow Problems
Patchy heat, one room cold, gurgling pipes, rooms that never reach the temperature they are set to, or pressure that keeps dropping.
Hydraulic faults → -
Wiring & Wiring Centres
The boiler never fires when a thermostat calls, the pump runs constantly, or the wrong room heats up when you turn a stat up.
Wiring faults → -
Boiler & Underfloor Together
The boiler fires and stops every couple of minutes, the radiators are hot but the floor is cold, or hot water and heating fight each other.
Boiler and UFH faults →
What You Can Safely Check Yourself
None of these involve tools, and all of them are things we would ask you about on the phone anyway. Working through them sometimes solves the problem outright, and if it does not, it tells us a great deal before we arrive.
Safe to check
- Is the thermostat actually calling? The set temperature needs to be above the current room temperature, and most stats show a flame or heating symbol when they are demanding heat.
- Batteries and schedule. Wireless thermostats go quiet when batteries die, and a programmer sitting in a setback or off period looks exactly like a broken system.
- Give it long enough. If it has been off, a screed floor needs hours, not minutes. Judge it the next morning, not twenty minutes later.
- Check the boiler pressure gauge. Cold, it normally reads somewhere around 1 to 1.5 bar. Repeatedly needing topping up points at a leak or an expansion vessel problem.
- Look at the manifold flow meters. These are the small clear gauges in a row. If they all read zero when the system should be running, nothing is circulating. Look only — nothing on the manifold should be touched or adjusted.
Leave these to an engineer
Anything on the manifold itself, including actuators, flow meters and the blending valve. Opening a wiring centre or any electrical enclosure, altering wiring, draining or refilling the system, and anything at all inside the boiler. Underfloor heating controls run at mains voltage in most homes, and boiler work is Gas Safe registered work by law. We are Gas Safe registered under number 519284.
Why a Working System Can Still Feel Broken
A good proportion of the callouts we attend are not faults. Underfloor heating behaves nothing like radiators, and systems get judged by the wrong standard.
Judge it by the room, not the floor
The floor temperature is the symptom, not the problem. A wet underfloor system is doing its job when each room holds the temperature it is set to, and a correctly running floor sits only a few degrees above room temperature while it does that. So a floor that feels neutral underfoot is normal and not a sign of a fault. A floor you can obviously feel warmth through usually means the flow temperature is too high, which is a fault worth attending to rather than a sign the system is working well.
The floor is a large, low temperature emitter. It warms a room gently over hours rather than blasting it in twenty minutes, and it keeps releasing heat long after it has switched off. That means turning it up when you feel cold rarely does anything useful, and turning it off when you go out often costs more than leaving it at a steady setting. Screed floors in particular are best run at a consistent temperature with a modest setback rather than being switched on and off.
It also means the honest test of a system is whether the rooms get to where you set them and stay there, not how warm the floor feels on the way. Turning a thermostat higher than you actually want the room does not get you there faster, it just overshoots hours later.
How We Find the Fault
We start with the history rather than the hardware: when it started, what changed just before, which rooms are affected and which are fine. That alone usually rules out two of the four groups above. From there we test at the manifold and the controls, checking what each thermostat is asking for, what the wiring centre is doing about it, whether each actuator is opening, whether every loop is flowing, and what temperature the water going into the floor actually is.
Most faults are found and fixed at the manifold or in the controls without touching the floor. Once it is working, we rebalance the system so the heat is even across every room, confirm it is performing before we leave, and tell you plainly what had gone wrong. You can read more about that on our repair and servicing page.
Underfloor Heating Fault FAQs
Why is my underfloor heating not heating up?
The four common causes are a control fault (the thermostat is not actually calling for heat, or the actuator on the manifold is not opening), a flow problem (air trapped in a loop, a failed pump or a stuck blending valve), a wiring fault (the demand never reaches the boiler), or a boiler setup problem (the flow temperature or controls are wrong for underfloor heating). Working out which group the symptom belongs to narrows it down quickly.
How long should underfloor heating take to warm up?
Much longer than radiators. A screed floor holds a lot of heat and typically takes two to six hours to come up to temperature from cold, and a similar time to cool down. A system that seems slow is often working exactly as intended and just needs its schedule setting differently rather than repairing.
Should an underfloor heating floor feel hot to walk on?
No. A correctly set up floor sits only a few degrees above room temperature, with a surface temperature of roughly 27C in living areas and a little higher in bathrooms. It should feel neutral or barely warm underfoot. A floor that feels genuinely hot usually means the blending valve is not limiting the flow temperature properly, which is worth attending to because it can damage floor coverings.
Why is one room cold when the rest of the floor is fine?
A single cold room points at that room's own circuit rather than the whole system. The usual causes are air trapped in that loop, an actuator that is not opening on that port of the manifold, a thermostat that is not calling, or that loop being throttled down at the flow meter so it never gets its share of the flow.
Can you repair an underfloor heating system that somebody else installed?
Yes. A large part of our repair work is on systems installed by other companies, including ones that have never worked properly since the day they went in. We diagnose it, fix it, rebalance it and explain what was actually wrong.
Is underfloor heating expensive to repair?
Most faults turn out to be in the manifold, the controls or the wiring rather than in the pipework buried in the floor, so they are usually fixed without lifting a single floorboard or breaking into screed. The expensive scenario, an actual leak in a buried loop, is rare.