Underfloor heating not getting warm diagnose by symptom
Floor staying cold? WhatsApp a photo of your manifold, or call 070 783 0224.
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Underfloor heating responds slowly, so "not warm" doesn't immediately mean something is broken. Yet there's often a clear cause. Choose the symptom below that most closely matches your situation. Each symptom shows what's usually wrong and what the next step is.
Short answer
If your underfloor heating is not getting warm, first check whether it affects one room or everything. One room cold: often a stuck thermostat head or air in that zone. Everything cold: check the pump, the boiler or heat pump and the settings. Everything lukewarm: often fouled pipes, an incorrectly set mixing valve or a supply temperature that is too low.
- Give it a few hours: underfloor heating is slow.
- Can you hear the pump? If not, see pump defect.
- Technician: call-out charge € 100 – € 165 excl. VAT (€ 121 – € 199.65 incl.).
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Leave your name and number and we'll call you. Prefer immediate contact? Call 070 783 0224 or message us.
One room or one zone stays cold
If it's one room or part of the floor, the problem is almost always at the manifold or in that particular circuit.
- Thermostatic head or valve stuck. The pin under the head sometimes stays pressed in after summer. Then the zone won't open.
- Air in the zone. Especially after topping up. How bleeding works is explained in bleeding underfloor heating.
- The flow meter is closed. You see no movement in the sight glass. Sometimes it has been accidentally turned off or is fouled.
- Room thermostat. In homes with a thermostat per room, that one thermostat may be the cause.
The entire floor stays cold
If everything stays cold, no hot water is circulating.
- The pump isn't running. Can't hear anything at the manifold, or is it humming? See underfloor heating pump faulty.
- The boiler or heat pump is not producing heat. Is there a fault or is the pressure too low? See boiler breakdown or heat pump breakdown.
- Settings. Summer mode, a thermostat on a low programme or a heating curve set too low.
Everything gets warm, but not warm enough
Lukewarm floors throughout the house indicate a problem with the system as a whole.
- Contamination. In older systems, sludge builds up in the pipes. Flow decreases and the floor becomes lukewarm. Flushing helps then.
- Mixing valve or mixing unit. With underfloor heating alongside radiators, a valve mixes the hot water with cold return water. If it's set too low or stuck, it stays lukewarm.
- Balancing. If each group does not receive the correct amount of water, short groups become warm and long groups do not.
- Insufficient output for the room. In a poorly insulated room or with thick carpet on the floor, the heat cannot escape properly.
Only warm near the manifold
If the floor is warm near the manifold and cold further away, the zone is not flowing properly. Air, a closed flow meter or contamination in that zone are the usual causes. Flushing each zone usually solves it. If the manifold is leaking, or the valves can no longer be moved, then replacing the manifold is the next step.
What does a technician for underfloor heating cost?
| Item | Excl. VAT | Incl. 21% VAT |
|---|---|---|
| Call-out charge: first 30 minutes including diagnosis | € 100 – € 165 | € 121 – € 199,65 |
| Flushing, balancing or replacing a component | price in advance after diagnosis | you hear the price upfront |
Guide prices from the PandFix price list (October 2026). Call-out charge is additional: €35 excl. VAT (€42.35 incl.), emergency €65 excl. VAT (€78.65 incl.). Evening or weekend: surcharge €80 excl. VAT (€96.80 incl.). Materials and extra hours only by agreement. You will always hear the price before we start.
Questions about underfloor heating not getting warm
How long does it take for underfloor heating to warm up?
Underfloor heating is slow. After turning up the thermostat it often takes a few hours before you feel a difference. If it stays cold after half a day, something is wrong.
Why isn't one room heating up?
Usually a thermostatic head or valve on the manifold that's stuck, or air in that zone. This can be fixed without opening up the floor.
Does my underfloor heating need to be flushed?
If all floors become lukewarm and the installation has been running for years, contamination may be the cause. After an inspection we'll tell you whether flushing makes sense.
Is my underfloor heating leaking if the pressure keeps dropping?
That's possible, but it could also be the boiler or the expansion vessel. See underfloor heating leak and pressure loss.
What does a technician cost?
The call-out charge of € 100 – € 165 excl. VAT (€ 121 – € 199.65 incl.) for the first half hour with diagnosis, plus travel costs. Further work only with your approval.
