chapter  18
Flat roofs
Pages 8

The cold deck has the insulation laid between the joists and the space above is ventilated to the outside air in order to prevent moisture condensing in the cold roof void.

WARM DECK

With the warm deck, the insulation is placed on top of the roof deck and the void between the deck and the plasterboard ceiling stays warm because it is protected by the insulation. On a warm deck roof, ventilation should not be provided to the enclosed voids.