Warm flat roof - Metal 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.

When using DuoRock 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. 
 
Free spanning capabilityMinimum DuoRock Roofing Board thickness equals the maximum through width divided by 3. 

Crown and trough position
Rockwool DuoRock Roofing Board must be laid with the long edge at right angles to the profiles of the metal deck. Butt joints should occur at the mid-crown position, except where cantilevering is applicable.
 
Cantilevering
DuoRock Roofing Board of 60 mm or greater thickness may cantilever over a trough, provided that the maximum trough width does not exceed twice the board thickness. For example, 70 mm thick DuoRock Roofing Board may cantilever over a maximum trough width of 140 mm.

Note: For 50 mm thick boards, the maximum trough width is one and a half times the board thickness (i.e. 75 mm).
 
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 DuoRock 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 DuoRock Roofing Boards to metal decks Rockwool Limited recommends the use of fasteners incorporating either a plastic tube washer or stress plate support thread.

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 DuoRock Roofing Board is also recommended in walkway and access areas. Advice should be sought from the membrane manufacturer on the options available. 

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.