Cold Deck Flat Roof Detail

When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off.

Cold deck flat roof detail.

Cold deck roof a cold deck roof is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof. Others would treat even steeper pitches as flat roofs. The 18mm roof grade deck is then fixed on top of the rafters leaving suitable air flow between the insulation and the deck. The sandwich warm deck roof is the most common type of flat roof.

The position of the insulation dictates which type it is. The definition of a flat roof according to bs 6229 is having a pitch less than 10 o to the horizontal however some in the industry would consider up to 15 o as their definition of a flat roof. The insulation boards in an inverted warm deck are laid over the structural deck and the waterproof covering. This is known as a cold roof because the roof deck and roof space are close to the external air temperature.

Details both in 2d and 3d to give a clear understanding. Introduction warm cold roofs this guidance offers guidance on the difference benefits between warm and cold roofs. In terms of the thermal design of a flat roof what are the options and the best practices of flat roof build ups. It is universally recommended that cold deck flat roof construction should be avoided.

In a cold roof construction the sarnafil membrane is installed directly to the structural decking usually timber with firrings to fall. Similar to the pitched roof a flat roof can be insulated as a cold or a warm deck. Flat roof details and information relating to insulating a flat roof. In the case of a flat roof insulation is usually either a rigid board above the deck or a mineral glass wool quilt immediately.

Ventilation is required for these roofs. This video shows the key features of a flat roof cold deck construction and how to draw the details to a scale of 1 10. This cold deck construction is considered problematic in the humid temperate climate of the uk where the effective ventilation of restricted roof voids may be impractical particularly in sheltered built up areas. The epdm rubber roof membrane is then installed using the contact adhesive onto the deck.

Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction this videos show detailed drawings. The recognised flat roof build ups for best design practices are. Inverted warm deck roof.