Warm Deck Flat Roof Construction Detail

Warm deck flat roofs can be constructed on most modern construction material types such as concrete timber and timber based sheets.

Warm deck flat roof construction detail.

Throughout the course of the year the roof deck and all below it is kept at a temperature close to that of the inside of the building therefore the roof structure is protected from extremes of hot and cold lessening the potential for damage caused by thermal movement. The insulation is immediately below the waterproofing layer. Warm deck flat roof the type of insulation for this is usually of a rigid type and the thickness will vary depending on the manufacturer s specifications. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading.

Inverted warm deck roof the insulation boards in an inverted warm deck are laid over the structural deck and the waterproof covering. Constructing a flat roof using epdm. Having a manual for warm flat roof construction with details and a summary of rules to follow helps. On a basic level flat roof construction comes in the form of roofing timbers or joists as they are more commonly known or steels that are laid across two uprights walls in most cases.

In a warm flat roof construction the insulation is positioned above the structural deck and no ventilation is required. The vapour control layer is above the decking but below the insulation. The insulation is placed below the waterproof covering and is either mechanically fixed or bitumen bonded on to the top of the deck. For additional stability you can also use steel joists that are built into one or both of the walls.

The construction of the flat roof is similar to that of the timber upper floor. 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. To use epdm for a warm deck flat roof construction solid closed cell roof insulation such as kingspan or celotex should be placed on top of the roof deck rather than in between the rafters. The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls.

Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. In a warm roof construction the principal insulation layer is placed above the structural decking resulting in the structural deck and support structure being at a temperature similar to that of the building interior. The sandwich warm deck roof is the most common type of flat roof.