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Third party certifications:
  • BSI Kitemark

    BSI Kitemark

    Certificate type


Lightweight, semi rigid slabs, suitable for thermal insulation of roof constructions.

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+44 (0)1656 862621 www.rockwool.co.uk

ROCKWOOL FLEXI® is a multi-use, dual purpose thermal and acoustic insulation product with a unique flexible edge along one side. The patented flexible edge ensures a perfect fit is maintained between the product and its supporting framework for easy installation and optimum effectiveness.

FlexI® slabs ensure essential tight fitting for thermal and acoustic integrity between frames in walls, partitions, floors and roofs, without the need for cutting or waste. Made from renewable volcanic rock, they are extremely fire resistant and significantly reduce the carbon footprint of a building.


  • Outstanding thermal, acoustic and fire properties.
  • FlexI® edge offers accurate fit to all widths.
  • Multi-application; fits all typical metal and timber stud spacing.
  • Wide range of thicknesses.
  • No waste.
  • Easy to handle and install without gaps.
  • Fire classification A1.
  • Can be used as a full fill solution in timber frame party walls to achieve zero effective U-value within SAP 2012.

General information
Uniclass 2015
Pr_25_57_06_56 Mineral wool slab insulationPrimary

K10/115 Metal stud partition system

K10/125 Metal stud partition system

K10/145 Wall lining system (metal studs)

K10/155 Wall lining system (metal studs)

K10/165 Wall lining system (metal framing)

K10/215 Suspended ceiling system

K10/30 Metal stud

K10/35 Wall lining on metal framing

K10/50 Suspended ceiling on metal framing

K11/115 Battened plywood floating floor

K11/125 Battened particleboard floating floor

K11/135 Battened oriented strand board floating floor

K11/145 Battened cement-bonded particleboard floating floor

K11/20 Battened particleboard floating floor

K11/25 Particleboard floating floor

K11/795 Wall lining on metal framing

K11/796 Metal stud partition system

K20/150 Battened timber board floating floor

K20/20 Battened timber board floating floor

K21/120 Battened wood flooring

K21/130 Battened wood floating floor

K21/140 Battened wood laminate flooring

K40/10 Suspended ceilings

K40/105 Suspended ceiling system

K40/285 Insulation

K40/55 Insulation

K45/13 Suspended ceiling system alterations

P10/10 Loft insulation

P10/140 Insulation fitted between rafters

P10/15 Insulation fitted between rafters

P10/170 Insulation to loft access hatches

P10/180 Insulation to water cisterns

P10/20 Insulation to loft access hatches

P10/240 Insulation fitted between floor joists

P10/25 Insulation to water cisterns

P10/250 Insulation supported between floor joists

P10/40 Insulation fitted between studs

P10/45 Insulation laid between floor joists

P10/50 Insulation supported between joists

Specification data - Mineral wool slab insulation
Product Reference



400 mm

600 mm


1200 mm


50 mm

60 mm

70 mm

90 mm

100 mm

120 mm

140 mm

180 mm

Standard product features


Mineral wool batts (slabs) to BS EN 13162 or Agrément certified.

Thermal Conductivity:

0.035 – 0.038 W/mK.

Reaction to fire class:

A1 to BS EN 13501-1.

Third party certifications
  • British Standards Institution (BSI) - certficate : Rockwool Flexi is CE and Key marked in accordance with BS EN 13162
  • British Standards Institution (BSI) - certficate : Non-combustible, achieving a classification of A1 in accordance with BS EN 13501-1
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