Timber Cold Flat Roof Construction

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

Timber cold flat roof construction.

In the warm flat roof construction there is insulation packed into every possible space where air can flow. A cold flat roof is one where the insulation is between or between and below the roof joists. As you may imagine there is a fair amount of weight involved here in terms of boards felt etc. Old asbestos roofs are often replaced with flat roofs.

Sizes of joists needed for flat roof construction. The insulation is below the deck but above the plasterboard. In a cold roof construction the sarnafil membrane is installed directly to the structural decking usually timber with firrings to fall. This ventilation is necessary to prevent condensation from forming below the roof deck which can.

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. This is used for refurbishment e g.