Cold Deck Roof Detail

This temperature criteria can be reduced to 40 f which corresponds to interior average conditions of 70 f 35 rh where high interior moisture loads due to spas indoor swimming pools and excessive humidification are.

Cold deck roof detail.

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. In a cold roof construction the sarnafil membrane is installed directly to the structural decking usually timber with firrings to fall. The insulation can be adhered mechanically fixed or loose laid. The vapour control layer is above the decking but below the insulation.

A warm flat roof or a built up roof bur is one where all the insulation is above the joists deck making them part of the warm fabric of the building. The insulation is immediately below the waterproofing layer. Introduction warm cold roofs this guidance offers guidance on the difference benefits between warm and cold roofs. This is known as a cold roof because the roof deck and roof space are close to the external air temperature.

Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction this videos show detailed drawings. In cold and very cold climates selecting a roof deck condensing surface temperature criteria of 45 f is very conservative. The 18mm roof grade deck is then fixed on top of the rafters leaving suitable air flow between the insulation and the deck. In a warm deck roof the insulation is positioned above the structural deck and no ventilation is required.

There are three recognised designs of flat roof construction. Cold deck roof 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. Ventilation is required for these roofs. This video shows the key features of a flat roof cold deck construction and how to draw the details to a scale of 1 10.

The epdm rubber roof membrane is then installed using the contact adhesive onto the deck. In a warm roof construction the principal thermal insulation layer is located above the structural decking resulting in the structural deck and support structure being at a temperature close to that of the interior of the building.