Underfloor Heating for Renovations

Why renovation UFH is not a new-build job

New builds open the floor, pour insulation and screed to a known level, and design door frames around the finished height. Renovations inherit uneven slabs, fixed thresholds, occupied rooms and mixed construction under one roof.

That is why overlay systems dominate retrofit work in practice: you add a thin heated layer on top of what is already there, connect to a boiler or heat pump, and keep the programme measured in days or weeks rather than a multi-month cure.

Screed still has a place when the floor is open anyway — extension, full dig-out, or a deliberate level change. It is rarely the default when people are living in the house.

The constraints that actually decide the system

Solid floors (most ground floors)

Overlay route: low-profile gypsum, XPS or similar boards on a prepared base, pipe in the system, thin finish. Height build-up is measured in tens of millimetres, not a full structural screed. Disruption is limited to the rooms being done.

Screed route: dig or raise levels, insulation, pipe, screed pour, dry and cure. Traditional cement mixes are often discussed with a rough “1 mm per day” drying rule of thumb for full cure — a 65 mm pour is a long wait before finishes. Liquid screeds can be thinner and faster but still need a proper programme.

Detail trade-offs: overlay vs screed · best system for renovations.

Joisted floors (usually upstairs)

Upper floors are almost always timber. Options typically include:

• •Aluminium heat-transfer plates between joists with pipe
• •Overlay boards on the existing deck if height allows
• •Structural UFH boards replacing the deck where the project allows

Insulation in the joist void, contact between plates and deck, and a clear route to the manifold decide performance. Do not assume ground-floor screed logic applies upstairs.

More: UFH upstairs renovation.

Disruption and living in the house

This is the reason overlay wins so often in Devon and Cornwall renovations. People still need the kitchen and living room. Digging out a solid floor, waiting for screed to cure, then finishing is a different scale of upheaval than a board system room by room.

Plan phasing: which rooms first, where the manifold lives, how pipe runs cross doorways, and whether temporary heat is required. A beautiful system that makes the house uninhabitable for two months is not a successful renovation plan.

Floor height and thresholds

Every millimetre of build-up hits door clearances, stair nosings, kitchen plinths and level access. Measure existing finished floor to underside of door and any step changes between rooms before choosing a system thickness.

Low-profile overlays exist because of this problem. If height is tight, say so at survey — do not discover it when the boards are on site.

Heat source: boiler vs heat pump

UFH and heat pumps pair well because both prefer low flow temperatures (often mid-30s to low-40s °C where design allows). A modern boiler can still drive UFH via blending at the manifold — common, slightly less efficient than a pure low-temperature system, usually workable.

• •Design room output at the flow temperature you will actually run
• •Do not assume “UFH means any heat pump will feel fast”
• •Steady controls beat deep setbacks — see not warming up fast enough

Devon & Cornwall renovation realities

• •Uneven historic slabs — overlays need a proper, level base; self-levelling may be part of the job
• •Low ceilings and tight doors — height is often the binding constraint
• •Mixed construction — solid ground floor + joisted first floor in the same project is normal
• •Solid stone / cob walls — UFH will not fix fabric heat loss; plan insulation and ventilation too
• •Oil / LPG to heat pump switches — low-temperature emitters become part of the whole-house plan
• •Conservation limits — external insulation and windows may be constrained; floors are often the freer upgrade path

Treat the envelope as one system. Spending heavily on UFH while leaving a naked loft and single glazing is how “the underfloor does not heat the room” stories start.

Cost thinking (renovation)

Supply-only rates and installed rates diverge sharply with access, levelling, manifolds, and whether screed is included. Overlay supply is often discussed in tens of pounds per m² depending on system; installed totals depend on labour, preparation and finishes.

Rule of thumb from industry practice: installation can sit in a similar order of magnitude to materials on many domestic jobs — but structural boards, full dig-outs and complex multi-zone manifolds push higher. Use planning bands from the calculator, then a site measure.

See also UFH costs 2026.

Recommended decision sequence

1. Map solid vs joisted rooms and any level changes
2. Measure height limits at doors and stairs
3. Decide which rooms stay occupied and the programme limit
4. Confirm heat source (existing boiler, new boiler, heat pump)
5. Choose system family per floor type
6. Design output at realistic flow temperature and finishes
7. Price supply, install, preparation and electrical/controls

Honest bottom line

Frequently asked questions