Flat roof

Warm deck - special systems

Protective layer Separating layer Waterproofing layer Thermal insulation Undercoat Falls in this layer

Loadbearing layer

Protective layer Separating layer Waterproofing layer Thermal insulation Undercoat Falls in this layer

Loadbearing layer

Fig. 10: Section through compact roof

Waterproofing layer Thermal insulation Vapour barrier Falls in this layer

Loadbearing layer

Waterproofing layer Thermal insulation Vapour barrier Falls in this layer

Loadbearing layer

Fig. 11: Section through uncoated roof

The conventional warm deck systems have given birth to special flat roof constructions - for reasons of aesthetics and/or specific products. These are single-skin roofs and so follow the same layering principle as a conventional flat roof: the waterproofing is seamless and is placed above the thermal i nsulation. A vapour barrier installed on the inside of the thermal i nsulation prevents damaging condensation. Here again, the necessary falls (min. 1.5%) can be produced in the loadbearing layer, in a layer specifically incorporated for this purpose or in the thermal insulation.

Compact roof

The compact roof evolved specifically from the use of cellular glass and only works with this material. All the layers apart from the protective layer or wearing course are fully bonded together and to the i oadbearing layer; together they provide the waterproofing, vapour-imperviousness and thermal insulation functions.

The i nsulation consists of vapour-tight cellular glass laid in a hot bituminous compound on the l oadbearing layer, and this also functions as the vapour barrier. The joints are simple butt joints filled with a hot bituminous compound. Two layers of bitumen roofing felt, again fully bonded, serve as a waterproofing layer. As on a conventional warm deck, a layer of gravel, paving flags, road surfacing material or planting serves as a protective layer or wearing course. The compact roof is an expensive system. However, with a loadbearing construction of in situ reinforced concrete (as rigid as possible) it guarantees a high standard of reliability with regard to preventing ingress of water.

Uncoated roof

Uncoated roofs are flat roof systems without a protective layer or wearing course. The omission of this protection means that the "exposed" roof covering must withstand various influences.

The make-up of the waterproofing can employ either bituminous or synthetic roofing felts (number of layers as for a conventional warm deck). In each case the manufacturer of the materials must confirm that the roof covering is suitable in terms of its resistance to ultraviolet radiation. It must also be incombustible (fire rating No. 6). The omission of the protection (ballast) also means that the roof covering is exposed to the wind. It must be ensured that all layers are fixed together (bonded or mechanically) such that the forces can be transferred. Mechanical fixings must be covered. Edges and junctions must be specially secured (wind suction). Uncoated roofs are sensitive to loads and are thus unsuitable for foot traffic. They must be approved - also by the local fire brigade. It is essential to check the waterproofing function of such roofs at regular intervals.

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