Should I fill the crawlspace drainage trenches before putting down a moisture barrier

Have you tried contacting NDS directly and asking for their advice/recommendation? Contact NDS

I'm suggesting the above as it is my understanding that their product is only for "external" property use ie On the outside of your crawlspace/foundation wall.

Below added after reading @Kenneth (feedback) comment:

I understand from NDS EZ brochures they state their drainage system is a gravel free solution, but I highly recommend back filling the trench in your particular situation with pea-gravel.

You can then breakout the foundation blocks locally (for a nice clean job I would use a core cutter, the foundation blocks will then naturally arch the opening you've made) to connect the new drainage system into an appropriate existing drainage system.

I wouldn't call that a typical base, but if it was properly compacted, it should work. The typical base is pretty much what you described:

• topsoil dug down to undisturbed soil and/or topsoil dug out then soil machine compacted
• 2" layer of crushed rock, machine compacted
• 2" another layer of crushed rock, machine compacted
• repeat until you get to 4" or the desired height (if above 4")
• 1" sand, leveled
• pavers

Note that in this system, you're not designing for permeability or drainage at all. If you are using pavers, this is hardscaping, and is meant to shed water, not absorb it. To properly shed, it needs to be properly sloped. This is true for the base layer as well.

The purpose of the base layer is to create a solid, stable surface. Ability to drain is desirable (to avoid frost heave) but that's secondary to providing a proper surface to shed water.

In your case, it sounds like you already have 4" of compatible material. I'd do the following:

1. remove pavers
2. rent a compactor and compact existing base
3. add additional base material and compact to get the slope you want
4. add sand
5. put pavers back
6. add locking sand to joints

the big catch here is that this will ultimately raise your patio next to your house several inches. If that's tolerable, you're good to go. If not, then you have to do the reverse...instead of adding material closer to the house, you need to take material and remove it further away from the house. This will reduce your total base at the outside edges, though. That may be acceptable in your case.