Retrofitting Underfloor Heating in an Existing Cornwall Home

Can You Add Wet UFH to an Existing House?

Yes — though the answer depends on your floor construction, available floor build-up, and budget. The main constraint is floor height: traditional screeded UFH adds 75–100mm to floor height, which is practical in a renovation project but impractical in a room with fixed door frames, stairs, or level access requirements. Modern low-profile systems solve most of these constraints.

We install wet underfloor heating as a retrofit in Cornwall homes ranging from granite cottages to 1970s bungalows. Here's what each scenario involves.

Option 1: Screeded Systems (Concrete Floor)

If you have a solid concrete ground floor (common in post-war bungalows, extensions, and barn conversions), screeded UFH is the most efficient option. Pipes are clipped to insulation board, covered in liquid screed to 65–75mm depth, and finished with your floor covering of choice.

Floor build-up: 75–100mm total (insulation + screed). You need this headroom above the existing slab.

Typical cost per m²: £50–£90 installed (materials and labour, not including floor finish).

Best for: Full ground-floor renovations, extensions, kitchen-diners, open-plan spaces.

Flow temperature: 30–40°C — ideal for heat pump efficiency.

Option 2: Low-Profile Overlay Systems

Low-profile UFH systems sit on top of existing floor surfaces and add as little as 15–25mm total floor height. Systems like Wunda or Uponor's Thin Systems use aluminium spreader plates with very small diameter pipes seated into pre-grooved insulation boards.

Floor build-up: 15–25mm. Compatible with most door frame heights when a 20mm threshold exists.

Floor finish: Tiles work directly over the system. LVT/vinyl works with most overlay systems. Engineered wood works with most. Solid wood typically not recommended (differential expansion).

Typical cost per m²: £65–£110 installed — slightly higher than screed due to materials cost, but lower disruption.

Best for: Existing concrete floors with limited headroom, kitchen refits, bathroom renovations.

Flow temperature: 35–45°C — still efficient with a heat pump, though slightly higher than screed systems.

Option 3: Suspended Timber Floor Systems

Many older Cornwall properties — terraced houses, Victorian cottages, pre-war bungalows — have suspended timber ground floors with a void beneath. UFH can be installed from below (between joists) without disturbing the floor surface, using aluminium reflector trays that press the pipe up against the floor boards for heat transfer.

Floor build-up: Zero — all installed beneath existing floor.

Access requirement: Either an accessible crawl space below floor (typically 450mm minimum) or a room that can be temporarily boarded access from above.

Efficiency note: Below-joist systems are less efficient than screed — heat dissipates in multiple directions. Use slightly higher flow temperatures (40–50°C) and accept slightly lower SCOP than a screed system. Still meaningfully better than radiators with a heat pump.

Typical cost per m²: £40–£70 installed (lower material cost, access-dependent labour).

Renovation and Extension Scenarios

The most cost-effective retrofit UFH installations happen when other work is already underway:

• Kitchen renovation — if the kitchen floor is being lifted, add wet UFH before relaying. Marginal cost over kitchen project alone: £1,200–£2,500 for a typical 15–20m² kitchen.
• Extension — all new extensions should have wet UFH designed in. The screed is going down anyway. We coordinate with your main contractor.
• Bathroom renovation — practical for wet room or ensuite tiling. Consider combining with low-profile system for main bathroom.
• Full ground-floor renovation — the opportunity to install wet UFH throughout ground floor in a single project, reducing per-m² cost and disruption.

What to Expect During Installation

A typical retrofit UFH project in a Cornwall kitchen-diner (20m²) with screeded system takes 2–3 days for the UFH element: one day for pipe layout and insulation, one day for screed. The screed then needs 7–14 days to cure before floor finish can be applied. The UFH manifold connects to your existing boiler or heat pump pipework — typically a half-day plumbing job.

We design the loop layout, pipe spacing (typically 200mm centres for rooms with windows, 150mm for bathrooms), manifold location, and flow calculations before installation begins. Over-specified is better than under-specified.

Pairing Retrofit UFH With a Heat Pump

If you're planning a heat pump installation within the next 5 years, designing the UFH manifold for heat pump flow temperatures now (rather than boiler temperatures) makes the future transition seamless. We specify manifolds with the appropriate thermostatic actuators, oversized pipe centres, and buffer tanks for heat pump compatibility from day one — even if the heat pump doesn't come until the following year.

Combined heat pump + UFH projects also qualify for the £7,500 Boiler Upgrade Scheme grant. We handle the application paperwork as part of the project. Contact us for a free survey and quote covering both elements together.