Free draining Cassette® balconies have soffits individually fixed to the rafters at typical 400mm centres. Each soffit has a gradient, usually sloped to the front of the balcony, so that rainwater will flow towards the front of the balcony, where it can freely drain.
Because each soffit allows the water contained within it to drain across the front edge, rainwater can be dispersed quicker and is less likely to puddle. This also makes the balcony less likely to block, like concrete, or steel frame balconies which depend on an individually, or small number of spouts.
The addition of a drip tray typically adds around 10% to the cost of an undrained balcony. This is well worth considering as this has significant benefits over open balconies with no soffits at all. Incorporating positive drainage to a Rain Water Pipe (RWP) typically adds a further 25% to the cost, and also makes the construction significantly more complex.