Elastomer bitumen membranes are commonly used as DPC (Damp Proof Course) in bridge decks.
Katepal's felts and built-up membranes have been used for waterproofing hundreds of thousands of square metres of bridge surface in Finland and the Nordic Countries. The Finnish Road Administration has a special approval procedure for membranes used in bridges. Katepal's bridge waterproofing membranes meet these requirements.
Trafficed surfaces on cold structures
Decks in courtyards intended for traffic, with no heated indoor facilities below are, so called, cold structures similar to bridges. The Finnish Road Administration SYL 6 guidelines may be applied in their waterproofing but often the traffic volumes are so small that somewhat less exacting standards may be applied. In such structures a waterproofing membrane is installed over the concrete deck and in most cases asphalt is laid directly over it. In addition to the trafficed areas, gravelled areas or different pavings may be built over the same waterproofing as long as water drainage functions well. If any green areas are to be incorporated, a root barrier should be applied to prevent plant roots damaging the waterproofing over time.
Trafficed areas and terrace structures - inverted structures
If there are any heated facilities below the trafficed deck or terrace structure, it is recommendable to use an inverted structure . In this case the structural member is built to have falls and/or a screed to create falls is applied over it. Waterproofing is applied to the sloping surface. Thermal insulation (usually XPS slabs = extruded polystyrene) is installed over the waterproofing and the surface layers are finally installed on top.
The structure must be dry and the concrete surface sufficiently even. To ensure adhesion, the surface is treated with a bitumen solution K-80 (primer). The primer should be dry before installing the membranes. In inverted structures it is recommended to attach the underlay throughout to the substructure, so that in case of leaks, the water is not able to spread over a large area between the concrete and the membrane. For waterproofing VE80 or VE80R class should be used. In practice TL2 + TL2 or TL2 + TL2 + TL2, and also TL2 + TL1 are possible.
The resistance to hydrostatic pressure and compressive strength of thermal insulation used should be as high as possible (usually XPS slabs). Between these slabs and waterproofing there should be a thin layer, which is as permeable as possible, ("sub-drain"), through which any water that has gathered between them can flow out via the drains of the inverted structure and the structure remains as dry as possible.
Water drainage can be improved, e.g. in the following ways:
Depending on use, the top surface can be concrete, stone paving, lawn or plants. Generally filter fabric should spread first on top of thermal insulation, to prevent cement or soil getting between the slabs.
The purpose of the surface layers is generally to channel most of the surface water directly into drains or otherwise out of the structure, to ensure that thermal insulation remains as dry as possible.