The load-bearing or substructure absorbs the loads acting on the decking and transfers them to the foundation. Their construction method must therefore be decided in connection with the choice of the pavement and the foundation and is based on the static requirements.
In the case of the supporting structure, it is important to ensure good weather protection, as its maintenance is usually made more difficult by poor visibility and considerable effort during replacement. Footbridges and decks "floating" above the terrain have better weather protection compared to constructions at ground level with direct contact with earth or water. The support surfaces of the upper components on the supporting structure should be chosen as narrow as possible, as a minimal contact surface makes it easier to dry quickly.
[...] In addition, top-side covers of the supporting timbers increase the service life of the timber construction. Puncture points of fasteners in these covers must be sealed as watertight as possible.
Source: Landscape Constructing – Material, Techniques, Building Elements; Astrid Zimmermann, Birkhäuser; Basel
