HardRock® Multi-Fix (DD) Underlay Slab
Thermal and acoustic insulation for flat roofs.
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Application(s)
- Roof
- Flat Roof
Product description
Designed to be installed with HardRock® Multi-Fix DD, HardRock® Underlay is a vital component in a ROCKWOOL flat roof solution. Manufactured from non-combustible stone wool, this robust product offers a thermal and acoustic foundation for a insulated flat roof system.
*Subject to application
- Euroclass A1 in accordance with BS EN 13501-1 Reaction to Fire rating
- Thermal conductivity 0.039 W/mK
- 70kPa Declared Compressive Strength
- Up to 120 minutes of fire integrity and insulation*
Product properties
| Name | Value | Unit |
|---|---|---|
| Declared thermal conductivity | 0.039 | W/mK |
| Reaction to Fire | A1 | Euroclass |
| Long term water absorption | WL(P) | kg/m² |
| Short term water absorption | WS | kg/m² |
| Product standard | EN 13162:2012+A1:2015 | |
| CE certificate number | 0751-CPR-393.0-01 | |
| Facing type, side 1 | No Facing |
Product variants
Areas of application
HardRock® Underlay Slab is suitable for use on the following construction types:
- Flat roof – in conjunction with HardRock® multifix DD
Documentation
Please select and download the documentation pertaining to this product. If you require any certification that is not listed here, please contact us via ukdocumentation@rockwool.com
HardRock Multi-Fix (DD) Datasheet
HardRock Multi-Fix (DD) is a BBA-approved dual-density insulation board suitable for various surfaces, including flat roofs. In addition to thermal comfort, it provides independently tested acoustic and fire resistance properties.
HardRock Multi-Fix (DD) BBA Certificate
Certificate No. BBA-21-5878
SUIS ROCKWOOL UK
Safe use instruction sheet ROCKWOOL stone wool insulation products
Republic of Ireland (ROI) Price List
Republic of Ireland Price List Feb 2026
UK Price List Feb 2026
UK Price List Feb 2026