Timber Cold Flat Roof Construction

Refurbishing an existing timber joisted flat roof which has no insulation.

Timber cold flat roof construction.

A cold flat roof is one where the insulation is between or between and below the roof joists. Sizes of joists needed for flat roof construction. The insulation is below the deck but above the plasterboard. One of the most essential considerations in a cold deck flat roof construction is the requirement for adequate ventilation in the form of a ventilated cavity of at least 50mm between the underside of the timber deck and the roof insulation below.

So any timber joists that are used need to be strong enough to support this weight. Old asbestos roofs are often replaced with flat roofs. This is used for refurbishment e g. As you may imagine there is a fair amount of weight involved here in terms of boards felt etc.

There must be an adequate void minimum 50mm between the deck and the insulation traditionally mineral wool to allow free movement of air and to prevent moisture vapour being transmitted from the building outwards where it could condensate in the roof. The major difference between the warm flat roof and the cold flat roof has to do with the air flow between the roofing timbers known as joists that help to hold up the roof. In a cold roof construction the sarnafil membrane is installed directly to the structural decking usually timber with firrings to fall.