XPS Insulation Board – Extruded Polystyrene Insulation Boards 6mm-50mm, 1200x600mm – Underfloor Heating, Floor & Wall Insulation

XPS insulation board is rigid extruded polystyrene foam, prized for its high compressive strength, low water absorption and consistent thermal performance. This 1200 x 600mm size is stocked in five thicknesses — 6mm, 10mm, 20mm, 30mm and 50mm — covering everything from a thin overlay under an electric heating mat to a proper thermal break beneath a solid floor.

XPS for Underfloor Heating

XPS insulation board is one of the most common underfloor heating insulation choices in the UK, because it does the one job that matters most: stopping heat from an electric mat or water pipe running down into a cold subfloor instead of up into the room. Laid directly onto a concrete or timber subfloor beneath your heating system, it cuts warm-up time, reduces running costs and stops "cold spots" caused by heat escaping downward. The closed-cell structure also gives useful impact sound insulation, so it doubles as an underlay for laminate and engineered wood floors even where underfloor heating isn't involved.

Choosing Your Thickness (6mm–50mm)

Thickness is the main decision on this board, and it depends on the job. 6mm and 10mm are the standard choice under electric heating mats and cable systems on an existing floor, where you can't afford to build up height. 20mm and 30mm suit water underfloor heating, colder solid floors, or where you want a stronger thermal break. 50mm is aimed at proper floor insulation and under-screed applications where thermal performance matters more than keeping a slim profile. As a rule, go as thin as your heating system allows and as thick as your floor build-up permits.

Floor, Wall & Loft Insulation Uses

Beyond underfloor heating, XPS insulation board works as general floor levelling and sound-impact underlay beneath laminate and solid wood flooring, as a moisture-resistant layer under tiles and screed, and as a lightweight insulation board for stud walls, dormers, vans and outbuildings. It's non-dusting, non-toxic, odourless and resists mould, fungal growth and rot, so it handles damp subfloor conditions that would degrade mineral wool or untreated timber packers.

Specification

Installation & Coverage

Installing XPS insulation board is straightforward: lay boards edge to edge directly onto a clean, level, dry subfloor, staggering joints on subsequent rows for stability. Boards can be cut to size with a sharp knife or fine-tooth saw. For underfloor heating, boards typically sit under the heating mat or pipe run and beneath the tile adhesive, levelling compound or screed. For flooring underlay use, boards sit directly beneath laminate or engineered wood. One 1200 x 600mm board covers 0.72m² — work out your total board count by dividing your room area by 0.72 and rounding up to allow for cuts and waste.