All new treated wood is ACQ. You need dipped fasteners and hardware but all
dock hardware is dipped already. Arsenic is a thing of the past. But that is
in US just noticed your up north.
Go with the treated. I have built many and never had a problem. Composite
requires 16OC centers or it will sag. Depending on your flotation system it
may be difficult to get framing that close together. You can span almost 3'
with a treated 2x6.

"Ron Tock" wrote in message
...
Need to build a new dock. Old one is just about done.
It'll be a floater like the old one.
The question is wheather pressure treated wood or
cedar is better. The problem with pressure treated is the arsnic content.
For a dock that swimmers and skiers will be sitting on and pulling
themselves up on, that's not so good. Cannot always get pressure treated
without arsnic.
How well does cedar hold up to extreme weather condiitions.
Fresh water, Canadian winters and all that.

TIA