If you want a really moldy mess and rotting wood under the new decking that would be the way to do it.
Remove the old decking, inspect the old floor joist.
Composite decking need the floor joist to be no more then 16" apart, if your going diaginal then they need to be no more then 12" apart.
Here's a cool tool I found that makes fast work when it come to ripping out decking boards.
I found mine at Northern Tool. http://www.thegutster.com/
The Following 2 Users Say Thank You to joecaption For This Useful Post:
just what joe said.. i had to replace composite decking on a deck built 2 years ago.. the joist spacings were all over the place and half werent even fastened properly.. had to add extra joists because the decking was running on a 45.. the old decking was saggin in the heavy traffic areas