How does underfloor heating work?

A warm floor sounds simple until you ask where the heat comes from and what sits under the boards. Drainplumb covers underfloor heating across Greater London, and the answer always starts with the floor, the heat source and the controls working as one.

If underfloor heating repair in City of Westminster is what you need, Drainplumb covers that as part of a plumbing and drainage business serving London. You describe the job at no charge and get a written price before any work starts.

Tell Drainplumb about your underfloor heating job anywhere in Greater London and get a written price before work begins.

How does underfloor heating work?

Underfloor heating works by warming the floor itself, so heat rises evenly through the room: a wet system circulates warm water through pipes laid under the floor, while an electric system heats cables or mats set beneath the floor covering.

Where people get underfloor heating wrong

Let's clear up the myths first. Underfloor heating is not a heater you switch on for twenty minutes. It's a slow system, and it works by holding a steady, gentle warmth. People who treat it like a fan heater get a cold room and a poor opinion of it.

It also does not suit every floor. A thick carpet with a heavy underlay blocks heat, and some timber floors need careful control of the surface temperature. And it isn't free heat. The system still needs a source, whether that's a boiler, a heat pump or the mains electricity behind an electric mat.

The biggest mistake is assuming the floor does all the work with no thought to what's under it. Insulation under the pipes or cables decides whether the warmth goes up into the room or down into the ground.

From the heat source to the floor surface

Here's the wet system, step by step. A boiler or heat pump heats water to a low temperature, usually far cooler than a radiator needs. A pump sends it to a manifold, which is the distribution point with a valve for each loop of pipe. Each loop runs under the floor in a snaking pattern and returns to the manifold. The floor surface warms, and the room warms from the ground up.

Electric systems skip the water. Heating cables or mats sit beneath the floor covering and warm up when the thermostat calls for heat. That makes them simple to fit in a single room, such as a bathroom. If you're after underfloor heating in Islington or elsewhere in London, the choice between wet and electric starts with the room and the floor build-up.

Controls matter as much as the pipes. A thermostat in each zone lets one room run warmer than another, and a floor sensor stops the surface getting too hot.

What decides which system suits a home

Four things settle it: the floor, the heat source, the height available and the room's use. A screed floor holds heat and responds slowly. A floating floor over timber joists responds faster, and needs a different layout. A new extension is the easy case, because the floor can be built to suit.

Retrofitting into an existing room is harder. A wet system adds floor height, so doors and thresholds may need to change. An electric mat adds very little height, which is why it's popular for bathrooms.

People often ask does underfloor heating cost a lot, and the honest answer is that it depends on the levers: the size of the area, the access, what's already in the floor, the type of system and the finish on top. That's why we give a written price after you describe the job, not a guess before.

How long it takes and the disruption to expect

We won't give you a number of days, because it depends on the room and the floor. An electric mat under tiles in a bathroom is a smaller job than a wet system through a whole ground floor, which means lifting the old floor, laying insulation and pipework, pouring screed and waiting for it to dry.

That drying time is the part people don't expect. Screed needs time before the floor covering goes on, and the heating is brought up gradually. Plan for the room to be out of use while that happens, and ask what the order of work will be before it starts.

What you can do yourself and what needs a plumber

You can set the thermostat and keep furniture from smothering the floor. There are no radiators to bleed. Everything under the floor is a job for a plumber. Connecting pipework to a boiler, setting the flow temperature and commissioning the manifold aren't DIY tasks.

A cold patch on the floor or a room that never warms usually points to an airlock, a stuck valve on the manifold or a fault in the controls. Describe it to us and we'll tell you what we'd look at first. You describe the job at no charge and get a written price before any work starts.