Compaction
Also known as: compacting, tamping
Compaction is mechanically pressing material together to remove air gaps and increase density and stability. Base rock, decomposed granite and soil are compacted so surfaces built on top stay firm and do not settle.
In simple terms
Compaction means packing material down hard so it stops shifting. You do it with a plate compactor or tamper so a base will support what you build — pavers, a path or a slab — without sinking later.
In depth
Compaction increases density by driving particles closer and expelling air and excess water. It is done in "lifts" (thin layers, typically 2–4 inches) because compacting too thick a layer at once leaves the bottom loose. Slightly moist material compacts best — at "optimum moisture content" particles slide into place; too dry or too wet and density suffers. Angular materials (crushed/base rock) compact to higher strength than rounded ones. The right equipment matters: plate compactors for granular base, rammers for trenches.
Why it matters
Skipping or rushing compaction is the most common cause of failed hardscape — settling pavers, cracked slabs and rutted paths all trace back to a base that was not compacted properly.
Common mistakes
- Compacting one thick layer instead of several thin lifts, leaving a soft base underneath.
- Compacting bone-dry material; lightly dampening it first reaches far higher density.
Examples & uses
- Compacting base rock under a paver patio.
- Tamping decomposed granite pathways in lifts.
- Preparing a stable sub-base for artificial turf.