Description
The 12.5mm NoMorePly Cement Coated XPS Board 1200 x 600mm (4′ x 2′) is the thickest board in the NoMorePly XPS insulated tile backer range at this sheet size, built around a high-performance waterproof extruded polystyrene core with roughly 1mm of polymer-cement mortar and glass-fibre mesh coating on each face. That construction is what makes it behave so differently from a plain cement board: the cementitious skin gives you a hard, tile-ready surface that takes adhesive directly, while the XPS core underneath does the insulating work. It is the right choice for kitchens, bathrooms and wetrooms, and it is recommended for tiling onto timber or light-gauge steel (LGS) wall frames, solid walls, and solid floors.
At 12.5mm thick the board carries an 11mm net XPS core, which is the deepest insulation layer in the 1200 x 600mm range and gives it the strongest thermal performance of the three. Each sheet weighs just 1.8kg, so a single person can carry, position and cut it with nothing more than a utility knife, yet the cement-coated surface will carry tiles up to 62kg/m², which covers large-format porcelain and natural stone. Insulated backer boards like this sit in a different bracket to plain cement boards and to timber substrates, and within that bracket the value is in getting the waterproofing and the insulation in a single, easy-to-handle sheet.
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Insulation and underfloor heating
This is where the board stands apart from standard tile backers and plywood. The 12.5mm version delivers an R-value of 0.37 (m²·K)/W and a U-value of 2.70 W/m²·K, with thermal conductivity between 0.033 and 0.036 W/mK (λd 0.034). In real-world use, the insulated XPS core helps stop heat escaping into a cold concrete slab or subfloor below. When paired with electric underfloor heating, more warmth is directed upwards into the room instead of being lost into the structure underneath, helping the floor heat up more quickly and efficiently. The board also helps reduce cold bridging from the substrate, which can limit condensation on cold solid floors and external walls. Its cement-coated surface is designed to tolerate both the operating temperatures and the chemical compounds used around electric underfloor heating systems, making it suitable as a direct substrate beneath them.
The board is 100% moisture resistant and designed to provide a waterproof tiled surface when installed and sealed correctly, which is the headline reason tilers reach for it over plywood. Plywood weakens, swells and can rot once it gets damp, whereas the XPS core has water absorption of just 0.2% by volume over a two-day immersion and zero capillary absorption, so it holds its strength and dimensions in a wet environment. That makes it dependable in showers, wetrooms and steam rooms where a timber-based board would eventually fail. When the joints are sealed with a bead of Mega Strength Adhesive during installation, the board build-up forms a waterproof surface with no need to tape the joints.
It is worth being clear here, because this board sits in the cement and non-combustible category but is not a non-combustible board. The XPS core is a polystyrene foam, so the board carries a Euroclass E reaction-to-fire classification, not an A1 rating. If your specification calls for a genuinely non-combustible A1 substrate, for example behind a wood-burning stove or as a fire-wall lining, you want a fibre cement board such as the 9mm or 12mm NoMorePly instead. The XPS board is built for insulation and waterproofing, not fire resistance.
The 12.5mm NoMorePly Cement Coated XPS Board is CE marked and UKCA marked, and the range is independently tested and certified low in emissions, with no EU controlled substances in either the foam core or the cement coating. NoMorePly is a UK brand by STS Ltd. When the installation guide is followed and the recommended STS fixings and adhesive are used, the board carries a lifetime guarantee.
Applications
- Tiling onto timber or LGS (metal) stud wall frames in bathrooms, wetrooms and kitchens
- Overboarding solid walls before tiling (dot-and-dab with flexible tile adhesive, then mechanically fixed)
- Overboarding solid floors as an insulated base for electric underfloor heating before tiling
- Wetroom and steam room wall linings where a waterproof, insulated substrate is needed
For overboarding stud walls and solid walls, NoMorePly recommends 10mm or 12.5mm boards, with this 12.5mm board giving you the most insulation and the most rigid result of the two. For a timber floor, the 10mm board is the usual call; step up to this 12.5mm board on solid floors or where you want the deepest insulation layer under heating. Remember the board provides a waterproof surface to tile onto but will not remove deflection or movement in a timber floor, so the floor itself must be sound and firmly screwed down first.
