Join Date: Jun 2015
Location: Victoria, BC, Canada
It's ok for the soil to get between the larger pieces, the point is not to have any particular spot packed deep with soil. The irregular surface of the filler provides that spacing. The filler (eg lava rock pieces) basically breaks up the packing so to speak.
You actually want those irregularities/granularities to prevent anaerobic pockets. Hence the use of ADA Power Sand. This stuff actually looks like horticultural pumice which is just expanded lava rock. Making it lighter weight and more airy.
If you have the budget, check out ADA Power Sand. Cheaper alternative is horticultural pumice (at least ten times cheaper). If you can screen it, use the biggest pieces from the bag.
I've read of some people using styrofoam or sponges under big rocks when hardscaping. This could work for your brick idea, but need to be careful that there isn't any sand or gravel that gets trapped under the sponge/foam which then puts undue pressure in one small spot.
There's also other folks out there who have done deep beds, but poke their substrate regularly to release trapped gasses.
I'm sure someone else can chime in on this!
Daisy Mae V
According to my husband, I have a habit of jumping right in!