140mm Rockwool Flexi Insulation Slab 1.2m x 400mm
ROCKWOOL Flexi is a stone wool insulation slab used across a wide range of domestic and commercial construction projects. It goes between studs in partitions and external walls, between joists in floors, and between rafters in roofs — and it stays put without slumping, cutting or fixing. The slab is made from natural volcanic rock spun into stone wool fibres, and it is manufactured with a flexible edge along one side that compresses on installation and then expands to grip the frame tightly from within.
This is the 140mm slab in the 400mm width — the primary specification choice for timber frame external walls, and the point in the Flexi range where the lambda value improves from 0.038 W/mK to 0.035 W/mK. That improvement matters in practice: at 140mm with a 140mm stud and a standard breather membrane, the build-up achieves a U-value of 0.28 W/m²K.
The slab is non-combustible to Euroclass A1 and is suitable for cold frame, warm frame and hybrid frame constructions. It is also used in suspended floor applications, where 140mm Flexi achieves a U-value of 0.22 W/m²K across all standard P/A ratios.
Benefits
- Primary specification for timber frame external wall insulation to meet Part L
- Improved lambda of 0.035 W/mK at 140mm and above — better thermal performance per millimetre
- U-values from 0.28 down to 0.20 W/m²K achievable depending on membrane and stud selection
- Flexible Flexi Edge for a tight friction fit — no cutting to width required
- Will not slump, even if timber studs shrink after installation
- Euroclass A1 non-combustible — the highest possible reaction-to-fire classification
- Also suitable for suspended floor applications — achieves 0.22 W/m²K at all standard P/A ratios
- Stone wool is vapour permeable, reducing the risk of condensation and mould
Good to Know
- Size: 1200 x 400 x 140mm; weight: refer to ROCKWOOL datasheet for pack details
- Thermal conductivity: 0.035 W/mK at 140mm and above, to BS EN 13162:2012 + A1:2015
- Reaction to fire: Euroclass A1 to EN 13501-1
- U-values range from 0.28 to 0.20 W/m²K depending on stud depth, breather membrane and VCL specification
- Install in accordance with current ROCKWOOL guidelines — visit rockwool.com/uk
- Always refer to the ROCKWOOL Flexi technical datasheet before installation
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140mm Rockwool Flexi Insulation Slab 1.2m x 400mm
140mm Rockwool Flexi Insulation Slab 1.2m x 400mm
ROCKWOOL Flexi is a stone wool insulation slab used across a wide range of domestic and commercial construction projects. It goes between studs in partitions and external walls, between joists in floors, and between rafters in roofs — and it stays put without slumping, cutting or fixing. The slab is made from natural volcanic rock spun into stone wool fibres, and it is manufactured with a flexible edge along one side that compresses on installation and then expands to grip the frame tightly from within.
This is the 140mm slab in the 400mm width — the primary specification choice for timber frame external walls, and the point in the Flexi range where the lambda value improves from 0.038 W/mK to 0.035 W/mK. That improvement matters in practice: at 140mm with a 140mm stud and a standard breather membrane, the build-up achieves a U-value of 0.28 W/m²K.
The slab is non-combustible to Euroclass A1 and is suitable for cold frame, warm frame and hybrid frame constructions. It is also used in suspended floor applications, where 140mm Flexi achieves a U-value of 0.22 W/m²K across all standard P/A ratios.
Benefits
- Primary specification for timber frame external wall insulation to meet Part L
- Improved lambda of 0.035 W/mK at 140mm and above — better thermal performance per millimetre
- U-values from 0.28 down to 0.20 W/m²K achievable depending on membrane and stud selection
- Flexible Flexi Edge for a tight friction fit — no cutting to width required
- Will not slump, even if timber studs shrink after installation
- Euroclass A1 non-combustible — the highest possible reaction-to-fire classification
- Also suitable for suspended floor applications — achieves 0.22 W/m²K at all standard P/A ratios
- Stone wool is vapour permeable, reducing the risk of condensation and mould
Good to Know
- Size: 1200 x 400 x 140mm; weight: refer to ROCKWOOL datasheet for pack details
- Thermal conductivity: 0.035 W/mK at 140mm and above, to BS EN 13162:2012 + A1:2015
- Reaction to fire: Euroclass A1 to EN 13501-1
- U-values range from 0.28 to 0.20 W/m²K depending on stud depth, breather membrane and VCL specification
- Install in accordance with current ROCKWOOL guidelines — visit rockwool.com/uk
- Always refer to the ROCKWOOL Flexi technical datasheet before installation
Original: $34.44
-65%$34.44
$12.05Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
ROCKWOOL Flexi is a stone wool insulation slab used across a wide range of domestic and commercial construction projects. It goes between studs in partitions and external walls, between joists in floors, and between rafters in roofs — and it stays put without slumping, cutting or fixing. The slab is made from natural volcanic rock spun into stone wool fibres, and it is manufactured with a flexible edge along one side that compresses on installation and then expands to grip the frame tightly from within.
This is the 140mm slab in the 400mm width — the primary specification choice for timber frame external walls, and the point in the Flexi range where the lambda value improves from 0.038 W/mK to 0.035 W/mK. That improvement matters in practice: at 140mm with a 140mm stud and a standard breather membrane, the build-up achieves a U-value of 0.28 W/m²K.
The slab is non-combustible to Euroclass A1 and is suitable for cold frame, warm frame and hybrid frame constructions. It is also used in suspended floor applications, where 140mm Flexi achieves a U-value of 0.22 W/m²K across all standard P/A ratios.
Benefits
- Primary specification for timber frame external wall insulation to meet Part L
- Improved lambda of 0.035 W/mK at 140mm and above — better thermal performance per millimetre
- U-values from 0.28 down to 0.20 W/m²K achievable depending on membrane and stud selection
- Flexible Flexi Edge for a tight friction fit — no cutting to width required
- Will not slump, even if timber studs shrink after installation
- Euroclass A1 non-combustible — the highest possible reaction-to-fire classification
- Also suitable for suspended floor applications — achieves 0.22 W/m²K at all standard P/A ratios
- Stone wool is vapour permeable, reducing the risk of condensation and mould
Good to Know
- Size: 1200 x 400 x 140mm; weight: refer to ROCKWOOL datasheet for pack details
- Thermal conductivity: 0.035 W/mK at 140mm and above, to BS EN 13162:2012 + A1:2015
- Reaction to fire: Euroclass A1 to EN 13501-1
- U-values range from 0.28 to 0.20 W/m²K depending on stud depth, breather membrane and VCL specification
- Install in accordance with current ROCKWOOL guidelines — visit rockwool.com/uk
- Always refer to the ROCKWOOL Flexi technical datasheet before installation
