Cold Deck Flat Roof

Traditionally flat roofs simply consisted of a structural timber deck with a waterproof covering directly applied to the top of the deck.

Cold deck flat roof.

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. Cold deck flat roof the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification. Alternatively battens can be secured to the underside of the joists and gmw fitted between these in much the same way as between the main roof joists. This is known as a cold roof because the roof deck and roof space are close to the external air temperature.

The underside of the rafters in this case will need to be finished with a suitable vapour control layer vcl and plasterboard to provide a suitable internal finish to the roof. The solution warm deck insulation. The breakdown warm roof vs cold roof. Traditional cold deck flat roof.

Ventilation openings either at. Cold deck flat roofs older roofs are typically built with a timber under deck providing the support for both the waterproof covering above and the thermal insulation below. A cold flat roof insulation requires more work taking off old boards and replacing them and the roof surface. Fortunately these days there is a better form of insulation available for your flat roof.

This specifically relates to cold flat roofs which require ventilation because they are more susceptible to high levels of condensation developing on the decks and external tiling or cladding. With a traditional roof insulation is likely to consist of mineral wool sheets suspended below the deck. 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. Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction this videos show detailed drawings.

The layer of insulation is essentially placed outside of the roof. Condensation occurs when warmer moist air meets colder surfaces. This design dates back many years and flat roof insulation was somewhat of an afterthought with this type of roof. Where a cold flat roof does incorporate insulation this is.

This system is called warm deck insulation and eradicates the condensation and venting issues associated with the cold deck system. A ventilation gap usually 50mm should be provided between the top of the insulation and underside of the roof covering to allow the air to flow across.