Cold Deck Roof

Traditional cold deck flat roof.

Cold deck roof.

This design dates back many years and flat roof insulation was somewhat of an afterthought with this type of roof. The breakdown warm roof vs cold roof. Traditionally flat roofs simply consisted of a structural timber deck with a waterproof covering directly applied to the top of the deck. 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.

These are cold deck and hot deck flat roofs and as the names suggest the difference is about how the roof handles insulation. A cold roof construction will normally comprise of a structural deck on joists or purlins with a ceiling layer fixed to the bottom of the joists purlins thereby creating an air layer or cavity within. The 18mm roof grade deck is then fixed on top of the rafters leaving suitable air flow between the insulation and the deck. Guidance advice on warm cold.

Older roofs are typically built with a timber under deck providing the support for both the waterproof covering above and the thermal insulation below. Ventilation is required for these roofs. The insulation in a warm deck roof is installed immediately below the roof membrane on top of the roof deck usually with a vapour control layer underneath the insulation. This is known as a cold roof because the roof deck and roof space are close to the external air temperature.

Contrasted with the cold deck roof this construction has a much lower risk of condensation as the void will be of a comparable temperature to the roof. Fortunately these days there is a better form of insulation available for your flat roof. Cold deck flat roofs. The epdm rubber roof membrane is then installed using the contact adhesive onto the deck.

Introduction warm cold roofs this guidance offers guidance on the difference benefits between warm and cold roofs. 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 flat roof insulation requires more work taking off old boards and replacing them and the roof surface.