Yep, I would go hardwood or composite if you are planning on keeping it any length of time.
In terms of the frame, are you concreting the posts into the ground? If so I would think about what wood you are using there, as standard 4x4 posts will rot out faster than anything else, you can slow that down a fair amount by using post savers or slow it even further by using a harder wood for the posts. I used 8x4 oak sleepers ripped in half, and then put post savers on as well for double protection.
Also does anyone have ballpark figures for longevity of fence post vs with post saver vs oak? Am hoping to do a 6x3m deck for my garden office this summer.
I'm also undecided on hardwood vs composite boards .
Yep, I would go hardwood or composite if you are planning on keeping it any length of time.
In terms of the frame, are you concreting the posts into the ground? If so I would think about what wood you are using there, as standard 4x4 posts will rot out faster than anything else, you can slow that down a fair amount by using post savers or slow it even further by using a harder wood for the posts. I used 8x4 oak sleepers ripped in half, and then put post savers on as well for double protection.