Flat roof insulation on concrete deck with loose-lying bituminous waterproofing

The thermal insulation will be realised by a board of rigid polyurethane foam (Eurothane Silver) with a core volume weight of ± 30 kg/m³ with a fire reaction Euroclass B s2 d0 (end use steeldeck).
The boards will be faced on both sides with a gastight and multilayered complex.
The declared thermal conductivity coefficient  λ_D = 0,023 W/mK.
The boards are subject to a permanent quality control conducted by an acknowledged institute. The production of the insulation boards is certified according to the ISO 9001:2000 standards.
The compression resistance with 10% deformation: > 120 kPa (1,2 kg/cm²).
The dimensions of the boards are 600 mm x 1200 mm. The insulation boards are laid loose on the vapour control barrier. The boards are installed staggered and with closed joints. The bituminous waterproofing is applied independently immediately after the installation of the insulation.
A heavy ballast (gravel, tiles or a monolith protection such as concrete or asphalt) will be installed on this in order to set off wind forces in compliance with the prescriptions given by the manufacturer of the waterproofing membrane. If tiles on tile carriers are used then the ground surface will be defined in such a way that the compression force on the insulation where the tile carriers are situated does not increase above one fourth of the pressure resistance of the insulation material measured with a compression of 10 %.
The necessity of a vapour control layer will be determined by a calculation or by the Technical Information 215 "HET PLATTE DAK" (the flat roof) of the WTCB. The specific guidelines incorporated in the Technical approval of the insulation material are applicable; when not available the general conditions of the note 215 are applicable.
The following surfaces and thicknesses have to be used: