Welcome @Shadow. It may assist others to reply if you are able to expand a little.
Sub tropical - coastal SE QLD & northern NSW?
What type of timber is currently failing and how was it treated? What type of maintenance did it receive if any?
Assuming you are looking to a similar timber style deck here is a discussion of one product type,
Are you able to expand on what environmentally friendly means in your circumstance? Some of the options for new decking include
- select seasoned and treated hardwood or oiled hardwood,
- wood composite timber bound by resins, may contain plastic polymers,
- fibre/pulp reinforced cement based boards,
- treated pine decking.
How the products are installed, and maintained is just as important as choosing the best option to suit the criteria. Personal experience suggests clay based pavers are the most durable and least maintenance, but they may not suit the site. All timber based products need some maintenance, which may not be environmentally acceptable depending on the product selected.
