SPC over underfloor heating — underlay and thermal resistance

Check the exact product and heating type

Water pipes in screed, embedded electric cables and heating film directly beneath flooring are different systems. Approval for one does not automatically cover the others. Flooring, heating and installation-material instructions must be compatible.

SPC describes the core construction. Floating installation is common, but not the only option: Barlinek’s Aura instructions also allow bonding products without an integrated underlay [1]. That permission cannot be extended to another collection.

Plank resistance is not the complete floor value

For floating installation, add the plank’s resistance to that of the separate underlay. If the declared figure already includes an integrated backing, do not add it twice. For bonding, check the adhesive and other relevant assembly layers.

A documented example: Arbiton Amaron Herringbone 5 mm has a declared R of 0.014 m²K/W [2]; Multiprotec Vinyl Click 1.4 mm has R = 0.008 m²K/W [3]. Their sum is 0.022 m²K/W. This is a calculation for the named components. Confirm current compatibility of the selected combination before use.

Similar underlay names can describe different specifications. Do not transfer an R-value from another version. Lower resistance helps heat transmission but does not independently determine household energy consumption or room warm-up time.

How to assess an underlay

• Compatibility: start with the flooring instructions, then compare products.
• R: low thermal resistance, accounting for the entire relevant assembly.
• CS: compressive strength, relevant to plank and joint support.
• DL and CC: repeated and long-term loading performance where required.
• Acoustics: distinguish sound inside the room from impact transmission through the structure.
• Moisture protection: establish whether a specified membrane or system layer is required.

The 400 kPa CS value declared for Multiprotec Vinyl Click [3] is a product specification, not a universal minimum for all SPC. Likewise, an underlay intended for laminate is not automatically suitable under thin vinyl.

Is thicker always better?

No. An overly compliant underlay can increase deflection and stress on joints. It cannot replace substrate levelling. A point-irregularity accommodation figure is not permission to exceed the flooring’s overall flatness tolerance.

Do not add a second underlay beneath a product with integrated backing unless expressly permitted. An acoustic underlay and a thin moisture-protection membrane have different functions; a membrane requirement must be checked separately.

Temperature, sunlight and rugs

Follow the product’s own limit. Barlinek specifies a maximum surface temperature of 27°C for the described SPC Aura system [1]. That is a model-specific example, not a single value for all vinyl.

Heating is not the only source of heat. Strong sunlight can create local temperature rises, and a thick rug may obstruct heat release. Check shading, rug placement and control requirements. A room-thermostat setting does not automatically enforce the surface limit at every location.

Subfloor and movement joints

SPC needs a dry, flat and stable substrate meeting its instructions. A waterproof plank neither dries the screed nor automatically protects lower layers against moisture. New heated screeds need the relevant commissioning procedure and acceptance checks before covering.

Plan perimeter gaps, doorways and heating-zone transitions. Fixed furniture must not accidentally pin a floating floor. There is no single gap width or maximum uninterrupted area suitable for every SPC model and room layout.

A checklist before installation

1. Record the exact flooring and underlay version.
2. Confirm approval for the heating system.
3. Establish whether the R-value covers the plank or the whole assembly.
4. Confirm the temperature limit and means of control.
5. Collect screed documentation and required measurements.
6. Mark fixed furniture, movement joints and strongly sunlit areas.
7. Agree heating restart, including adhesive curing where applicable.

A suitable SPC assembly can have very low resistance. Incorrect underlay, installation or temperature control can undermine that advantage. Checking the complete system matters more than a general “ideal for underfloor heating” claim.