Cold Deck Flat Roof Construction

Flat roof design guide.

Cold deck flat roof construction.

In the case of cold roofs the residential flat roofs have the waterproof placed directly on the deck and any insulation would be placed above the ceiling. Warm roof insulation ensures the entire roof structure is insulated meaning a warm deck roof is more energy efficient than a cold roof. A cold deck is constructed as follows. A cold flat roof insulation requires more work taking off old boards and replacing them and the roof surface.

Warm cold and inverted. For both a warm and cold flat roof a vapour control layer must be installed. This arrangement allows the deck to become cold. There are three recognised designs of flat roof construction.

In a cold roof the thermal insulation is laid between the joists below the structural deck. Less thermally efficient than a warm roof construction cold roof construction remains the most common form of construction for existing flat roofs. Although not recommended today and actually banned in scotland until recently cold flat roofs were fairly common. Flat roof u value 0 18 w m2k 2 warm deck flat roof the type of insulation for this is usually of a rigid type and the thickness will vary depending on the manufacturer s specifications.

In a cold weather such roofs are inherently prone to condensation which can cause material decay and deterioration. Building regulations state that a ventilation gap of at least 50mm must be in place between the insulation and the underside of the flat roof deck. As the insulation is not required to take any loads quilts and other loose fill materials can be used as well as rigid insulation. Thickness varies according to the manufacturer s specifications.

In the case of a flat roof insulation is usually in the form of either a rigid board above the deck or a fibrous quilt immediately above the ceiling depending on the type of roof construction.