Warm flat roof - Timber deck
 

The boards are to be laid strictly in accordance with the manufacturer’s recommendations, staggered, butt-jointed and mechanically fastened through the vapour control layer to the deck. Alternatively the boards can be bonded in hot bitumen.
 
When using Hardrock Dual Density Roofing Boards, ensure that the dense layer is used on the upper side towards the membrane. This is clearly marked on the boards as ‘This side up’.
 
The use of small pieces of insulation board should be avoided.
 
Appropriate stop battens should be installed to protect open edges of boards.
Day joints must be formed at the conclusion of each section of work to seal exposed edges of insulation boards and prevent damage.
 
Membrane installation
The membrane should be installed strictly in accordance with the manufacturer’s specification and fastening requirements for wind uplift. 
 
Built-up high performance bituminous membranes
Built-up membranes should not be laid on insulation boards at temperatures below 5° unless special care is exercised.

Mechanical fastening of insulation 
Single ply mechanically fixed systems
Where the complete roofing system is mechanically fastened (for example single ply), Rockwool Limited recommends that a minimum of one mechanical fastener is used per board (or part thereof) to locate and secure the boards during installation.

This recommendation is based on independent wind uplift tests to determine the wind-induced load on mechanically attached Hardrock Dual Density boards. 

The tests conclude that for both the field area and the edge region of flat roofs sufficient stability is achieved when using one fastener. For the corner region of flat roofs, it is universal practice in such vulnerable areas to increase the number of membrane fasteners per m2, and also to reduce the distance between the rows of fasteners.

For the mechanical fastening of Hardrock Dual Density Roofing Boards to timber decks Rockwool Limited recommends the use of fasteners incorporating either a plastic tube washer or stress plate support thread.
 
Fully bonded membrane system
Where the membrane is fully bonded to the insulation surface (e.g. with bitumen or adhesive), the number of mechanical fasteners per board should be determined by wind loading calculations conducted by the membrane manufacturer.

Additional roof loads
Plant and machinery
Wherever possible, any roof-mounted plant, such as air handling and refrigeration units, should be positioned on independent upstands bearing directly onto the substrate.
 
Walkways and access areas
Additional protection to spread the load on Hardrock Dual Density Roofing Board is also recommended in walkway and access areas. Advice should be sought from the membrane manufacturer on the options available. 
  
Adhesive bonding of Hardrock Dual Density
Hot applied adhesive
Hardrock Dual Denaity may be fully bonded in hot bitumen to a suitable vapour control layer.

Cold applied adhesive
Hardrock Dual Density may alternatively be bonded to suitable vapour control layers using approved PU and cold bituminous adhesives.

The advice of the membrane manufacturer should be sought when specifying all aspects of the vapour control layer, fasteners, waterproof covering and construction of walkways.

Additional notes for Build-up felt, Pour and Roll
The membrane must be bonded in accordance with BS 8217: 1994. A ventilating sheet (3G) is not required.

The advice of the membrane manufacturer should be sought when specifying all aspects of the vapour control layer, fasteners, waterproof covering and construction of walkways.