Compactor roller or plate compactor: which to use

On a serious job, two or three compaction machines are usually used, not one. Each covers an area the others cannot reach — and the uncompacted areas are exactly where settlement appears.

Comparison

Machine	Where it works	What it compacts	Limitation
Tandem roller	open surfaces, asphalt	finishing layers, surfacing	does not reach edges and areas next to obstacles
Single-drum vibratory roller	soil and ballast fills	thick layers, at depth	too big for small spaces
Plate compactor	edges, block paving, yards	thin layers	low output on large areas
Trench rammer	narrow trenches	fills, vertically	only very small areas

The tandem roller

Two smooth drums, without aggressive vibration. It gives a finished, uniform surface. It is the machine used to compact asphalt, straight after the paver, while the mix is still hot.

It is also used on ballast layers for the final finish, after the vibratory roller has done the heavy work.

The single-drum vibratory roller

A single drum that vibrates strongly. The vibration transmits energy deep down, so it compacts much thicker layers than a smooth roller.

It is the machine for fills: platforms, earthworks, roads at the foundation stage. It is not used on finished asphalt, because the vibration would break up the structure.

The plate compactor

The machine people underestimate the most. It is used exactly where the roller cannot reach: next to fences, next to kerbs, around manholes, on narrow paths and when laying block paving.

The area the roller does not reach is the area that sinks first. If a job does not also have a plate compactor on hand, the edges will develop bumps.

The trench rammer

It jumps vertically, with a small foot. For service connection trenches, where the fill has to be compacted in depth, in a space a few tens of centimetres wide.

How they combine on a real job

On a platform:

1. The vibratory roller compacts each layer of fill.
2. The plate compactor does the edges and the areas around manholes.
3. The tandem roller gives the finish, and when paving it compacts the asphalt surface.

In a service connection trench:

1. The rammer compacts the fill, in layers.
2. The plate compactor finishes at the surface.
3. If asphalt was cut, the roller compacts the patch.

The mistake you pay for

Using a single machine for the whole job. A large roller in a small yard leaves the edges uncompacted. A plate compactor on a 2,000 square metre platform takes a week and still does not compact at depth.

The machine is chosen according to the area, not according to what happens to be available.