flat roof green roof system
for flat roofs
Driveways on roofs require both a load-bearing system build-up and a load-bearing roof construction. Moreover, vehicular traffic on a roof deck induces very significant horizontal forces and torsional movements through steering, breaking and accelerating, that must be absorbed.
Driveways on rooftops require both a stable construction and adequate load-bearing capacity. If the structure cannot withstand very heavy loads, then the rooftop (with its driveway) will show warnings regarding the load limitations (e.g. "maximum permissible axle load of lorry up to 3.5 tons"). If such limitations apply, the construction can be "streamlined" under certain conditions. As wheel loads lead to enormous concentrated loads due to their relatively small surface area, sufficient load distribution has to be available. This can be achieved through the use of load-distributing plates or through sufficiently thick substrata.
The stone thickness should be selected in accordance with the loads. Lesser loads (e.g. cars only), do not call for the paving to be as strong as if used with higher loads. When both car and lorry traffic occur, the rolling structural loads can lead to perversions. Selecting a larger stone thickness will result in a larger bearing surface between the stones, which will do more to counteract perversions.
Steering, breaking and accelerating on driveways can lead to enormous horizontal forces being created. In order to direct these forces away from the roof’s waterproofing, measures such as laying slide bearings may be required. The forces are then contained by stable surrounds.