Absolutely! You first need to remove the old decking material from the existing joists if exposed to the elements, (as mentioned in Can DekTek Tiles Be Installed Over My Existing Decking (wood/composite)? before you can apply the new DekTek pavers. It is also a good idea to remove the dirt and grime from the top of the joist so that the adhesive will bond to the joists better. The best way to do this is to sand it with a belt sander or a power washer with enough pressure will also work.
The next step in installing DekTek Tile on your existing wood joists, is that you need to add on a sister joist. This allows enough space for the tiles to bare on. For decks that can support 11 lbs per sq. ft. then a 2” x 4” sister joist is sufficient. For decks that need additional structural support you may need to add a larger sister joist such as a 2” x 8” or 2” or 10”. Refer to your local lumber company for weight calculations and joists size.
If you’re concerned that your deck joists may not be strong enough, you’ll need to consult your local lumber company to make sure your framing is sufficient for supporting 11 lbs. per sq. ft. dead load.