On commercial sites, drainage rarely fails with drama. It degrades through small, cumulative mistakes: contaminated aggregate, sluggish soak-away, and yard edges that feel "spongy" after rain. The irritating part is that your stone can be perfectly acceptable, yet fines still migrate upward and occupy the voids meant to move moisture away. A competent separation layer preserves those voids while resisting soil intrusion, so performance stays consistent for longer. In this article, we will discuss how that balance is achieved and what to scrutinize on site.