Underfloor Heating Installation London: Costs, Suitability and Installer Guide
Underfloor heating transforms how a room heats — gentle, even warmth from floor level. But in London properties, the practicalities require careful consideration. This guide covers wet vs electric systems, suitability for different property types, and the full cost breakdown.
Wet (Hydronic) vs Electric Underfloor Heating
Underfloor heating splits into two fundamentally different systems:
- Wet (hydronic) systems: A network of water-carrying pipes embedded in or laid on the floor. Connected to the property's boiler (or a heat pump). The floor is warmed by circulating hot water — typically at a lower flow temperature (35–45°C) than a conventional radiator circuit (60–70°C). More expensive to install, cheaper to run. Suited to whole-house installations and new builds.
- Electric systems: A heating mat or cable laid under the floor finish, wired to a thermostat. No pipework, no connection to the boiler. Cheaper and far simpler to install. More expensive to run (electricity costs more per kWh than gas). Ideal for individual rooms — bathrooms, kitchens, extensions — rather than whole-house heating.
Suitability for London Properties
London's housing stock presents specific challenges for underfloor heating:
- Wet UFH in existing London houses: Ground floor installation is most practical — wet UFH pipes are embedded in a screed above the existing concrete or suspended floor. The screed depth (typically 65–80mm) adds significant height, which is a problem in London properties with low floor-to-ceiling heights (particularly ground floors of Victorian terraces already limited by period construction). Upper floor wet UFH is possible but involves lifting all floorboards and significantly modifying the structure.
- Electric UFH in London flats: Electric heating mats (typically 3–6mm thick) fit under tile or LVT finishes with minimal height addition. This makes electric UFH practical for bathroom or kitchen retrofits in flats where any height gain from a wet screed would be prohibitive.
- New build and major renovation: Wet UFH is standard practice for new London houses and apartment building common areas where it can be designed in from the start.
Floor Build-Up Height — the London Challenge
Height gain is the critical practical constraint in London retrofit UFH installations:
- Electric mat (under tile): 3–6mm — negligible, compatible with most door clearances
- Electric mat (under LVT/engineered wood): 6–12mm — may require door adjustment
- Wet UFH in screed: 65–100mm — requires door replacement and may reduce usable ceiling height below 2.3m in ground-floor rooms of Victorian terraces
- Wet UFH on overlay system (low-profile, no screed): 25–30mm — a compromise that avoids deep screed but sacrifices some thermal efficiency
Compatible Floor Finishes
Not all floor finishes suit underfloor heating. The best conductors (lowest thermal resistance) allow heat to transfer efficiently to the room:
- Ideal: Ceramic tile, porcelain tile, natural stone. Low thermal resistance — heat transfers quickly and the finish retains warmth.
- Good: Luxury vinyl tile (LVT), engineered wood (max 18mm board, max 0.15 m²K/W total resistance)
- Avoid: Thick carpets and underlay (high thermal resistance — dramatically reduces UFH efficiency), solid hardwood above 18mm
Running Costs
- Electric UFH: At current electricity prices (~28p/kWh), electric UFH costs significantly more to run than a gas wet system. An electric bathroom mat (300W, 2 hours per day) costs approximately £60/year. Electric UFH as a primary heating source would be expensive.
- Wet UFH: Running costs are comparable to or lower than a radiator system, depending on boiler efficiency and control quality. Wet UFH at 35–45°C flow temperature runs more efficiently from a condensing boiler (which condenses more effectively at lower flow temperatures) — potentially 10–15% more efficient than the same boiler running radiators at 70°C.
Combination with Existing Boiler
A wet UFH system connects to the existing combi or system boiler, typically via a manifold and thermostatic mixing valve (which blends the flow temperature down from the boiler's standard circuit temperature). Most modern combi boilers are compatible with UFH. Worcester Bosch, Vaillant, and Ideal all explicitly confirm UFH compatibility in their installation manuals.
Cost Breakdown for London Installations
- Electric UFH (single bathroom, supply and install): £500–£900
- Electric UFH (kitchen, supply and install): £700–£1,200
- Electric UFH (full ground floor, 30m²): £1,500–£2,500
- Wet UFH (ground floor of London terraced house, 50m²): £3,500–£6,000 including screed
- Wet UFH (whole house, new build or major renovation): £6,000–£10,000+
Frequently asked questions
Can underfloor heating go under existing floors in London?
Electric heating mats can go under new tile or LVT laid over an existing floor — no structural disruption required beyond laying the new floor finish. Wet underfloor heating under existing floors requires either lifting all floorboards and installing on top of the subfloor (adding 65–100mm of screed height), or using a low-profile overlay system (25–30mm). In most existing London properties, electric UFH for individual rooms and wet UFH only for ground-floor extensions or major refurbishments is the practical approach.
Is underfloor heating better than radiators in a London home?
Wet underfloor heating runs at lower flow temperatures (35–45°C vs 60–70°C for radiators), which suits heat pumps and increases condensing boiler efficiency. It provides more even, comfortable heat and frees up wall space. However, it is slower to respond than radiators (heat-up time 1–3 hours vs 15–30 minutes) and is harder to retrofit in existing London properties with suspended timber floors. For bathrooms and newly built extensions, UFH is generally preferable. For whole-house retrofit in an occupied London property, radiators are usually more practical.
Does underfloor heating work with a combi boiler?
Yes — wet underfloor heating works with a combi boiler via a thermostatic blending valve (UFH mixing valve) that reduces the flow temperature from the boiler circuit to the appropriate UFH temperature (35–45°C). All major combi boilers (Worcester Bosch, Vaillant, Ideal) are compatible with UFH. Electric underfloor heating has no connection to the boiler and is entirely independent.