Underfloor heating transforms the comfort of a London home and works with almost any floor finish. Here is what you need to know about system types, installation timing, and realistic costs.
Underfloor heating (UFH) has moved from a luxury feature to an expected specification in high-quality London renovations. It provides even, radiant heat from the floor — warmer feet, no cold spots, no radiators on walls — and pairs well with the open-plan layouts that characterise most rear extension projects. For stone, tile, or polished concrete floors in particular, it transforms what would otherwise be a cold surface into a comfortable one.
This guide covers the two system types, what each requires, installation timing, and realistic costs.
Two system types: wet and electric
Wet (hydronic) underfloor heating A network of plastic pipe (usually cross-linked polyethylene, PEX or PE-RT) embedded in a screed or within a low-profile system board, carrying warm water from a heat source — boiler or heat pump. The water temperature is lower than a radiator system (typically 35–45°C flow temperature versus 65–75°C for radiators), which makes UFH particularly well matched to heat pumps.
Wet UFH is the correct choice for whole-floor installations, large areas, and any project where a heat pump is either installed or anticipated. Running cost over time is lower than electric. Installation cost and complexity is higher.
Electric underfloor heating A mat of resistive heating cable embedded in tile adhesive or a thin self-levelling compound. Heats quickly (15–30 minutes to reach temperature), simple to install, suitable for single rooms. The limitation is running cost: electric heating is significantly more expensive per kWh than gas or heat-pump heated water. Appropriate for bathrooms and small kitchens; not cost-effective as the primary heating system for a whole property.
Installation timing
This is the most critical practical consideration. UFH must be installed before the floor finish is laid. For wet systems embedded in screed, the screed must be poured and cured before any floor finish — typically 28 days for standard screed, less for fast-drying compounds. This means:
- —Wet UFH must be on the programme before structural completion — ideally at first-fix stage
- —Electric mats can be installed just before tiling, giving more flexibility
For a rear extension project, the wet UFH pipework should be laid and pressure-tested before the screed is poured. Any changes to the floor layout after screed is down that require lifting the screed are expensive and disruptive.
Floor finishes and UFH compatibility
Not all floor finishes work equally well with UFH:
| Floor finish | UFH compatibility | Notes |
|---|---|---|
| Stone (marble, limestone, slate) | Excellent | High thermal mass, excellent heat distribution |
| Porcelain and ceramic tile | Excellent | Low thermal resistance, heats quickly |
| Engineered timber | Good | Must be specified as UFH-compatible; max 27°C floor temp |
| Solid timber | Limited | Most species unsuitable — check with manufacturer |
| LVT / luxury vinyl | Good | Most products UFH-compatible; check manufacturer spec |
| Carpet | Poor | Insulates against heat transfer; increases running cost significantly |
For solid timber floors on a wet UFH system, the combination is generally not recommended — timber expands and contracts with temperature and moisture change, and the cycles of heating and cooling accelerate this movement. Engineered timber (a plywood or HDF base with a hardwood veneer) is more stable and suitable if specified correctly.
Zoning and controls
A UFH system should be zoned — each room or area controlled independently by its own thermostat or zone valve. A open-plan kitchen-dining-living space might be a single zone; bedrooms should each be separately controlled. Under-specification here — one thermostat for a whole floor — leads to overheating in some areas and underheating in others.
Modern UFH controls (Heatmiser, Honeywell, Salus) allow scheduling by zone, remote control via app, and integration with smart home systems. Wireless thermostats avoid the need to chase walls for thermostat cables after the wet trades are finished.
Heat source compatibility
Boiler (gas or oil): A standard combi or system boiler can run a UFH system, but requires a low-loss header or blending valve to reduce the flow temperature to UFH-appropriate levels (35–45°C). Most modern condensing boilers modulate effectively to UFH temperatures.
Heat pump (air source or ground source): UFH is the ideal heat emitter for a heat pump. Heat pumps deliver their best efficiency (COP) at low flow temperatures — exactly what UFH requires. The combination is the gold standard for energy efficiency in a new or substantially renovated London home.
Existing radiator system: A mixed system (UFH in the new extension, radiators in the rest of the house) is common and works well with a correctly designed manifold and appropriate controls.
Realistic costs
| Scope | Approximate cost (exc. VAT) |
|---|---|
| Electric mat, single bathroom (6–8m²) | £600 – £1,200 (supply and install) |
| Wet UFH, rear extension only (25–35m²), new screed | £3,500 – £6,500 |
| Wet UFH, whole ground floor (60–80m²), new screed | £7,000 – £13,000 |
| Wet UFH, whole house (150m²+), including manifold and controls | £15,000 – £28,000 |
These costs cover the UFH system, screed, controls, and commissioning. They exclude the heat source (boiler or heat pump) and any structural work.
ASAAN installs wet underfloor heating systems as part of rear extension and whole-house renovation programmes. If your project includes a new structural slab or screed, we specify UFH at the programme stage so it is embedded correctly and commissioned before floor finishes are laid.
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