Flat Timber Roof Detail

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

Flat timber roof detail. This is used for refurbishment e g. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Usually a flat roof is built with a slight slope to provide some drainage. Cad details document name pdf dwg download all cad construction details 37 1 mb 3 4 mb mc01 identification of roof areas 694 kb 167 kb mc01a single layer underlayment 678 kb 302 kb mc01b double layer underlayment 711 kb 322 kb mc02 vent pipe flashing 626 kb 349 kb mc03 valley.

A cold flat roof is one where the insulation is between or between and below the roof joists. The flat roof shown above shows warm deck roof construction. Normally a slope of inch per foot is used. The construction of the flat roof is similar to that of the timber upper floor.

The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls. A cavity closer should be provided to the top of the walls to prevent fire spread and to stop damp air entering the roof space. The insulation is below the deck but above the plasterboard. 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.

The steels or rsj s rolled steel joists are often built into one or both walls to give added stability to the roof structure. Flat roofs can be used to create box shapes cantilevered into daring overhangs or can be planted to create usable vegetated gardens. In this type of construction the insulation is placed below the waterproof covering and on top of the roof deck and vapour barrier. Where a new flat roof abuts an existing external wall the joists can be hung on metal joist hangers which are fixed to a horizontal timber plate wall bolted to the wall.

Rainer barthel 1 loadbearing structure matthias beckh mark. A roof which is approximately flat is called as a flat roof. For additional stability you can also use steel joists that are built into one or both of the walls. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading.

Having a manual for warm flat roof construction with details and a summary of rules to follow helps. This ensures that the deck holds a warm temperature during the winter. The abutment detail of a flat roof is vital in order to prevent moisture penetration.