Pack Gravel in Layers
Depending on the type of soil, most paths, patios and walls require an 8- to 12-in.- deep compacted base of gravel. But if you just dump 8 in. of gravel into a trench and run a plate compactor over it, only the top few inches will be fully compacted. The uncompacted gravel will settle later, creating waves in the wall or path. For a fully compacted base that won't settle, add the gravel in 2- or 3-in.-deep layers, and run the plate compactor over each layer before adding the next one.