Rockwool Flat Roof Insulation

Posted on October 27, 2016 by CCF


Flat Roof


A flat roof with a single-ply membrane (SPM) typically consists of a structural deck with a vapour-control layer, thermal insulation, and a polymeric single-ply membrane top sheet. With proper installation and good maintenance, these durable materials have a life expectancy of up to 30 years. Materials that are lightweight and easy to handle help reduce the costs. They need less structural support and are cheaper to transport. For a safer installation, try bonding the membrane to the substrate with adhesives or hot-air welding.


HARDROCK® Multi-Fix (DD)

ROCKWOOL HARDROCK® Multi-Fix (DD) is a versatile flat roof solution which carries with it exceptional acoustic and fire resistance properties. Suitable for any building type, HARDROCK® Multi-Fix (DD) is compatible with an array of flat roof systems including; Single-Ply, EPDM, green roof, bitumen & liquid membranes.

Acoustic Performance

The inherent acoustic properties of ROCKWOOL HARDROCK® Multi-Fix (DD) can reduce or even eliminate the need for additional acoustic mass layers when meeting all but the most demanding specifications for the reduction of airborne and rain noise.

Fire Performance

ROCKWOOL HARDROCK® Multi-Fix (DD) offers a high level of fire protection and is classified as non-combustible in accordance with UK Building Regulations and the LPCB achieving a European ‘reaction to fire’ classification of A1.

Thermal Performance

ROCKWOOL insulation offers excellent thermal properties and will help reduce energy usage and costs. Made from a renewable and plentiful resource it is a practical choice to maximise the performance of your building.


Meeting U-Values

PIR Substitution Chart


The table below can be used to find equivalent ROCKWOOL products across various applications that will achieve the same thermal performance as the PIR boards indicated.


Please note: The above u-value calculations are guidance notes only, provided by Rockwool, for further information and performances outside of this table, please see the ROCKWOOL online U-value calculator or alternatively contact