Timber Cold Flat Roof Construction

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.

Timber cold flat roof construction.

A cold flat roof is one where the insulation is between or between and below the roof joists. In a cold roof construction the sarnafil membrane is installed directly to the structural decking usually timber with firrings to fall. Refurbishing an existing timber joisted flat roof which has no insulation. As you may imagine there is a fair amount of weight involved here in terms of boards felt etc.

This ventilation is necessary to prevent condensation from forming below the roof deck which can. In the warm flat roof construction there is insulation packed into every possible space where air can flow. 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. 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. Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction this videos show detailed drawings. Sizes of joists needed for flat roof construction.