For a free draining deck surface, you must incorporate a gradient in one direction of your deck. Most decks (other than ground level) utilise a post and beam construction. The support posts (normally placed at no more than 1800mm) centres sit in or on a concrete footing, the later utilising a metal connector / shoe.
Q-Deck PLUS Multi-purpose deck posts material is ideal for use as support posts and is also available shaped (3m long classic post), should you want to incorporate a shaped newel above deck level.
Beams are the main horizontal support members of the deck and when connected as pairs (as recommended) can provide both great strength and an ideal place for housing Q-Deck PLUS newel posts, should you require balustrades. A pair of timbers are either bolted (recommended) or screwed (with, for example, Q-Deck Plus timbertite heavy duty landscaping screws) to the support posts at a height to suit whilst also very easily incorporating a desired gradient for water run off (1:80).