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Installation Advice

Double Sided Impax Board

Where the wall to be sheeted is an external building wall, the sheets must be manufactured from a fibre cement sheet which is bonded on each side to a sheet of Zincanneal. Correct specifications are essential and pressure laminating must occur in a quality controlled factory environment.

Double sided sheets provide a stable panel which will not distort under varying ambient surface temperatures.

Single Sided Impax Board

For internal wall and ceiling linings, the Impax Board is manufactured from a single sheet of fibre cement, bonded to a single sheet of Zincanneal. The Impax Board can then be fixed direct to timber or metal framing.

Correct specifications are again essential and pressure laminating must occur in a quality controlled factory environment.

Where there is an existing wall or ceiling, sheeted with either fibre cement or plasterboard, single sided Impax Board can be directly fixed over the existing sheeting, provided that the existing framing structure can support the additional weight.


Recommended framing components are timber and/or 1.2 mm thick galvanised metal.

Specification variations can be made with framing design approval from an authorised Engineer, which is based on the application and system area weights.

Wall frame spacing shall be at 600 mm maximum centres, ceiling frame spacings at 400 mm maximum centres, with additional framing required behind all sheet joints.


For timber: 10 x 30 mm CSK head Type 17 screws
For steel: 10 x 30 mm CSK head TEK or Drill Point screws

Fixing Spacing

All sheets are to be fixed at 200 mm centres around the sheet perimeter, with a minimum of 15 mm edge clearance and at 400 mm centres through the field of the sheet.

All sheets are to be pre-drilled with a pilot hole 1.0 mm oversize of the nominated screw diameter.

Treatment of Screw Heads

All screws are to be countersunk and filled with Ciba Geigy 125 Araldite or similar and flush sanded.

Site Storage

All site materials must be stored under cover, in a dry and level location until fully installed.


It is recommended that as much cutting as possible, be undertaken with a diamond blade wet cut saw bench in a factory environment.

When sheets are site cut, the edge of the cut Zincanneal should be painted with a metal primer.

The blade must firstly cut through the Zincanneal and then through the fibre cement to minimise delamination. Pre-drilled and cut to size sheets can be supplied ex factory by arrangement.

For saw blade cutting in a clockwise direction, see the following diagram:

saw blade cutting

Always cut at slow speed with a diamond blade on a wet table saw.

The blade must cut through the steel sheet first and then the fibre cement sheeting which is much softer.

Cutting through the fibre cement sheeting first and then the steel sheet will promote bond separation at the cut edge due to the hammering effect of the blade.