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Underfloor Heating

Wet underfloor heating designed and installed properly: screed systems for new builds and extensions, low-profile overlay boards for retrofits, zoned controls throughout. Radiator-free walls, even warmth underfoot, and a system that pairs beautifully with a heat pump.

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By the Surrey Heating team

Gas Safe registered engineers · West Molesey, KT8

·Updated 17 October 2026·5 min read·Underfloor Heating

Wet underfloor heating turns the whole floor into a radiator: warm water circulates through pipework under the surface, heating the room gently and evenly from the ground up. No cold corners, no radiators eating wall space, no scorched-air feeling — just a floor that's pleasant to walk on and a room that holds an even temperature. It's the heating people fall for in an extension and then wish they'd put everywhere.

The installation route depends entirely on the floor you have. In a new build or extension, the pipework is clipped over insulation and buried in screed — the gold-standard system, with the mass of the screed storing and radiating heat beautifully. In an existing room, digging up the floor is rarely sensible, so we fit low-profile overlay systems: pre-routed boards that sit on the existing floor and add as little as 15–20mm of height, with the door trimming and threshold details planned honestly before anyone commits. Both are genuine underfloor heating; they just suit different jobs, and we'll tell you plainly which yours is.

Underfloor heating runs at low water temperatures — typically 35–45°C — which makes it the natural partner for a heat pump and an efficient match for a modern condensing boiler. We design every system room by room: pipe spacing calculated for the heat loss, a manifold for proper zoning, and straight advice on floor coverings before anything goes in — tile is superb, engineered wood fine, thick carpet a poor match.

Screed or overlay: which wet underfloor heating suits a retrofit?

For retrofits, a low-profile overlay system is usually the right call: pre-routed boards laid on the existing floor, adding only 15–20mm of height. Screed systems suit new builds and extensions where the floor is being built anyway, because burying pipes in screed means excavation in an existing room.

The trade-offs are honest ones. Screed systems win on heat storage and output — the thermal mass holds warmth and the pipes sit in ideal contact with the slab — and they cost less per square metre when the floor build-up is happening regardless. Overlay systems win everywhere else in a retrofit: no excavation, far less mess, a faster job, and quicker response too, since there's less mass to heat before the room feels it.

The detail that decides many Surrey retrofits is floor height — even 18mm means doors trimmed and thresholds managed, all solvable if planned. In the period houses around Surbiton and Thames Ditton with suspended timber floors there's a third route: between-joist systems fitted with the boards up, keeping the finished floor level exactly where it was.

What does wet underfloor heating cost per square metre?

Budget £50–£75 per square metre installed for a screed system going into a new build or extension, and £80–£120 per square metre for a low-profile overlay retrofit. A typical 25m² kitchen-diner extension lands around £1,500–£2,000; a whole ground floor retrofit runs £4,000–£8,000.

What moves the number: room size (small rooms carry the manifold and controls cost over fewer metres, so the rate is higher), the system type, and the work your heat source needs. Worth saying plainly, too: UFH costs more to install than radiators and less to enjoy — it spreads heat evenly, lets the thermostat sit a degree lower for the same comfort, and frees every wall in the room. In an extension, where the screed is being poured anyway, the premium over radiators is modest and never regretted.

Does underfloor heating work with wood floors and carpet?

Tile and stone are the best floor coverings for underfloor heating, engineered wood works well within the manufacturer's temperature limits, and carpet is workable only if the carpet and underlay together stay under about 2.5 tog. Thick carpet on a heavy underlay smothers the output and wastes the system.

The principle is simple: everything above the pipes is insulation between the heat and your feet. Porcelain and stone conduct superbly, which is why UFH feels so good in kitchens and bathrooms; engineered wood is dimensionally stable and happy when the surface temperature is limited to around 27°C, which we set at the controls; solid hardwood is riskier, as wide boards can cup over heat.

Tell us your intended flooring at the survey, because it changes the design — pipe spacing tightens under higher-resistance coverings. And if your heart is set on deep carpet in one room, we'll say honestly that a radiator may serve it better than a smothered floor circuit.

Can you retrofit underfloor heating in one room?

Yes — single-room retrofits are common and sensible, especially kitchens, bathrooms and extensions. An overlay system goes over the existing floor, connects back to your boiler or heat pump via a compact single-room manifold or blending valve, and runs on its own thermostat, independent of the radiators.

The kitchen-diner is the classic case — the room where the family actually lives, often extended, often tiled, and tiles without UFH are cold tiles for half the year. Bathrooms are the other favourite, best done during a full bathroom installation, with the floor already up.

One honest caution: mixing UFH and radiators on one central heating system is entirely normal, but the UFH circuit must be blended down to its lower temperature and zoned with its own controls — not teed off a radiator loop and left to cook the floor. And if a heat pump is in your future, each room converted to UFH makes that system cheaper and more efficient.

What’s included

Screed & low-profile systems
Heat-pump ready by design
Room-by-room zoning
Extensions, retrofits & single rooms

When you need this

You're building an extension and the screed is going down anyway — the cheapest UFH you'll ever buy
You're refitting a kitchen or bathroom and want warm tiles instead of cold ones
You want radiators off the walls in a living space to free up furniture layout
You're planning a heat pump now or later — UFH's low flow temperatures are its perfect match
You have a period home with suspended timber floors and want between-joist UFH done by someone who's met joists before
One room never gets warm and you'd rather fix it elegantly than add another radiator

How it works

1. Survey and floor assessment
We check the floor construction, heights, door clearances, your heat source and intended floor coverings — the four things that decide the right system.
2. Room-by-room design
Heat-loss calculation per room, pipe spacing and circuit layout to match, manifold position agreed, and a fixed written quote with the floor build-up stated in millimetres.
3. Preparation
Insulation or overlay boards laid, perimeter detail set, and on timber floors the structure checked and prepared. Doors and thresholds planned before pipe goes down, not after.
4. Pipework and manifold
Circuits laid to the design and pressure-tested before they're covered — screed is poured or boards are closed only over pipework proven tight.
5. Controls and commissioning
Manifold connected and blended to the design temperature, zones wired to their thermostats, and the system balanced circuit by circuit. Screed systems get a proper gradual first heat-up.
6. Handover
A plain-English run-through of the controls, the floor-covering temperature limits in writing, and the design pack kept on file for whoever fits your flooring.

Underfloor Heating prices in Surrey — from

Indicative starting prices including VAT. The exact price depends on the property, system and parts — call for a firm, fixed quote.

Screed system (new build/extension), per m²
From £50
Pipework, insulation, manifold and controls — poured with your floor
Low-profile overlay retrofit, per m²
From £80
Adds 15–20mm height; no excavation of the existing floor
Single room (kitchen or bathroom)
From £1200
Overlay system with its own zone and thermostat, typical room size
Kitchen-diner extension (~25m²)
From £1500
The most popular job we do — in the screed as the extension is built
Whole ground floor retrofit
From £4000
Multi-zone manifold, blended from your boiler or heat pump

Surrey Heating vs the alternatives

Honest comparison against the national chains and insurance-style cover plans. Pick what works for you — but pick with the facts.

Criteria	Surrey Heating	Chain / cover plan
Design	Room-by-room heat-loss calculation sets pipe spacing	Kit-sellers: one spacing for every room in Britain
Floor height honesty	Build-up stated in millimetres, door trimming priced in	"Low profile" discovered to mean 30mm on fitting day
Floor coverings	Straight advice — including "use a radiator in that room"	Everything's compatible until the output disappoints
Integration	Blended and zoned properly with your boiler or heat pump	Teed off a radiator loop and left to overheat the floor
Aftercare	Local team who designed it, balanced it, and answer for it	Online kit with a helpline; your builder learns on your floor

In Surrey

Local picture

Underfloor heating work tracks the building work, and around here that means kitchen-diner extensions — Molesey, Walton, Esher and Weybridge are full of them, and pipework in the new screed is the cheapest, best UFH money buys. The period stock of Surbiton, Kingston and Thames Ditton brings the trickier, more satisfying jobs: suspended timber floors where between-joist or low-profile overlay systems keep original floor levels intact. And with heat pumps arriving across Surrey, UFH's low flow temperatures make every installation a down-payment on an efficient future system. We're based in West Molesey (KT8) and design, install and commission the whole thing ourselves — no kit posted to your builder with best wishes.

FAQ

Underfloor Heating — your questions, answered

How much height does retrofit underfloor heating add to the floor?+

Low-profile overlay systems typically add 15–20mm including the board, before your floor covering goes on top. That usually means trimming door bottoms and managing thresholds — straightforward if planned, which is why our quotes state the full build-up in millimetres and include the door work. On suspended timber floors, a between-joist system can avoid any height change at all.

Is wet underfloor heating better than electric mats?+

For anything beyond a small bathroom, usually yes. Electric mats are cheap to install and sensible for a few square metres of en-suite floor, but they heat with electricity at full price, so running costs climb quickly with area. Wet UFH costs more up front and runs from your boiler or heat pump at a fraction of the running cost per unit of heat. Our rule of thumb: electric for a small single bathroom, wet for kitchens, living spaces and whole floors.

Does underfloor heating work with a normal boiler, or only heat pumps?+

It works well with both. A modern condensing boiler actually runs more efficiently feeding UFH, because the low return temperatures keep the boiler condensing. The manifold blends the water down to the 35–45°C the floor needs regardless of source. The heat-pump connection is simply that UFH is the ideal partner — a heat pump is most efficient at exactly the temperatures UFH wants — so UFH installed today makes a future heat pump cheaper and better.

How long does underfloor heating take to warm a room?+

Depends on the system. Overlay boards respond in well under an hour — not far off a radiator. Screed systems are slower, often two to three hours from cold, because the slab itself heats up; the flip side is the slab then radiates steadily for hours. In practice screed systems run on schedules rather than on-off blasts, and the room simply stays at temperature.

Can underfloor heating go under my engineered wood floor?+

Yes — engineered wood is the wood flooring designed for the job, stable over heat where solid boards can cup and move. The conditions: the floor surface temperature is limited, typically to 27°C, which we set at the controls, and the board manufacturer's UFH guidance on thickness and underlay is followed. Tell us the flooring at the design stage and we tighten the pipe spacing to compensate for the wood's resistance, so the room still hits temperature on the coldest week.

Can you put underfloor heating over suspended timber floors in a period house?+

Yes, and around Surbiton, Kingston and Thames Ditton we do it regularly. The usual route is a between-joist system — insulation and heat-spreader plates fitted with the boards lifted, preserving the original floor level — or a low-profile overlay where a small height gain is acceptable. Insulation below the pipes matters enormously on timber floors, and we check the void's structure and ventilation while we're in there.

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