Clayboard

*Residential Grade Clayboard (Formerly KN30 Grade) - Designed for concrete depths up to 1000mm. For concrete depths over 1000mm Commercial Grade Clayboard should be used. Please call for details.

Clayboard is a void former suitable for use under Residential and Commercial reinforced concrete slabs and groundbeams. It has been approved by the NHBC as an appropriate void former underneath residential properties. It has also been awarded British Board Of Agrement certification.

Clayboard is a biodegradable honeycomb core set between lightweight polypropylene facings. When installing Clayboard it must be kept dry by encasing it in polythene, enabling the Clayboard to support the weight of the wet concrete and steel reinforcement. Once the concrete is poured and set, moisture is introduced using the voidpak system. This will soften the Clayboard core to make it collapse, therefore leaving a void to accommodate soil expansion without exerting pressure on the structure above.

Residential Clayboard has a nominal compressive strength when dry of 30kn/m2 and can support concrete up to 1 metre deep. When wet the Residential Grade Clayboard will collapse under just 3kn/m2 of force.

Clayheave is the phenomenon caused by changes in the water content of shrinkable clay soils. They expand when wet and shrink when dry. It causes ground movement that can create major structural damage unless foundations are designed to take account of changes in soil volume.