Plate compactor buying guide

A plate compactor, or wacker plate, is a motorized device with a smooth, heavy compactor plate attached to a vibrating mechanism. Driven by an electric or fuel-powered engine, these devices are used to compact filling materials, layers of aggregate ready for tarring, finished tarmac and concrete, as well as to bed down paving stones.

For outside use, although a manual equivalent might be sufficient for small-scale work. However, a powered plate compactor is essential once the going gets tough. Modern construction materials such as interlocking concrete blocks, coated materials and tarmac forming road surfaces,  as well as areas set to receive concrete, need to be thoroughly compacted in order to provide stability.

Steam rollers (or, more accurately, road rollers) used on very large surfaces are no good in cramped or awkward spaces, for example in landscape design.

It's these intermediate cases where the plate compactor comes in as it is compact and offers manoeuvrability.

The design and operation of the machine are simple: its key feature is a thick sheet of reinforced steel, curved away at the edges. This plate is interchangeable and can be coated in rubber, polyurethane or various other materials depending on the nature of the surface you're working on.

A vibrating mechanism connected to an electric or petrol-powered motor makes up the rest of the machine. The device is steered and controlled via a handlebar on an articulated bracket. An emergency stop is provided in case of accidents.

Here are the key criteria for choosing your plate compactor:

• motor power (in kW)

• compaction force in kN (kilonewtons)

• maximum speed in metres per minute

• vibrations per minute (vpm)

• vibration force in m/s²

• compaction depth in cm

• width and length of plate

• noise level in decibels (dB)

• maximum angle of tilt (for use on sloping ground)

Note that vibration force is the amplitude of vibration felt by the machine operator as a result of the plate's oscillating acceleration. This is expressed in m/s² (metres per second squared).

This point should be considered carefully; anti-vibration gloves are recommended when using a plate compactor, and where possible exposure to vibration should be kept within reasonable limits. Taking regular breaks is always good practice.

Electric plate compactors are uncommon, the reason being the constant risk of flattening the power cable. They're also limited in what they can be used for. However, some landscape gardeners use them for small-scale compacting work.

Since nobody's brought out a battery-operated model to date, the only other option is a petrol model. Here are the important points with an electric plate compactor:

• motor power 750 - 1000W

• maximum speed 5 metres per minute

• vibration speed around 2800 vpm

• compaction force 5kN

These are the real deal when it comes to plate compactors. There are two main types:

• unidirectional - lighter, easier to manoeuvre models

• bidirectional (reversible) - heavier machines

Often, a wacker plate can prove bulky and difficult to transport. Manufacturers have struck gold recently by designing models complete with a handy trolley that allows them to be used with ease by one operator; other models have fold-away wheels.

For optimum compactor efficiency, you can sometimes get side extensions to suit tricky surface layouts.

Most plate compactors have an option to stay in one place for particularly stubborn patches.

Before you get going with your plate compactor, here are a few guidelines you should be aware of:

• Always wear safety shoes with a steel toe-cap

• Wear anti-vibration gloves and a noise-cancelling helmet

• Compaction plate work shouldn't be attempted on slopes greater than 25%

• When working on a moderate slope, walk backwards and start at the lowest point

• Never put yourself downhill of the machine: it's not worth the risk of it slipping and falling on you

• When transporting the machine, ensure that it is stowed as securely as possible

Constant vibration, harder and more yielding surface materials, dusty environments, rain, muddy conditions… Plate compactors can be exposed to some extreme wear and tear. For this reason, it's a good idea to check the state of the bottom of the vibratory plate regularly and clean after every use.

The air filter on petrol models is liable to clog fairly quickly, and should be replaced as soon as you notice this.

Plate compactors with a petrol engine in fact require various additional maintenance (spark plug, appropriate motor oil, etc.).

The general state of the machine should be checked each time before you use it (check for loose bolts etc.).