Sink-run material

Best for

The wet run and the sink base — the case aluminium composite exists for.

Watch out

It is a construction choice, not a finish: it does not change how the kitchen looks, so it is easy to cut and regret.

Relative cost

Below honeycomb.

Consequential work

This is the moisture-zone decision the whole kitchen hangs on; settle it before fronts and finishes.

Best for

The wettest positions, and where weight matters as well as water.

Watch out

Cut edges and fixings need the right detail; it is not forgiving of on-site improvisation.

Relative cost

The highest of the three.

Consequential work

Fixing method and edge treatment must be specified, not left to the installer.

Best for

A middle path where a timber substrate is wanted and exposure is real but not constant.

Watch out

Grade and glue line vary widely between suppliers — the name on the sheet is not a specification.

Relative cost

Below ACP.

Consequential work

Requires the actual grade to be named in the specification, not just 'waterproof plywood'.

Plywood only where the room's specification names this grade. Otherwise the wet sink run is aluminium (ACP or honeycomb), or protected P6 where ALUMAX's listed protections are recorded and ALUMAX's site measurement finds P6 suitable; aluminium where it does not.

Not pictured here: protected P6. Unprotected board swells at the edges under a kitchen sink and fails from the inside, so ELS allows P6 there only with ALUMAX's listed protections — foil, sealed edges and penetrations, a raised bottom edge and a leak inspection — and where ALUMAX's site measurement finds P6 suitable; where it rules P6 unsuitable, the sink run is aluminium.