Most drainage problems don’t start with pipes. They start when stone meets weak ground, and the fine particles creep upward, slowly filling the voids meant to carry water away. Once that happens, you get ponding, rutting, and messy rework. A good filter layer keeps water moving while stopping that “mud migration” from taking over the base. It’s a simple idea, but the details matter. In this article, we will discuss how it works, how to choose it, what factors influence cost, and how to install it properly.