Essex Groundworks Supplies Ltd Home PageAbout Essex Groundworks Supplies LtdView  a map of our location

Ground Movement - Claymaster

Claymaster is a compressible expanded polystyrene, specially manufactured within a critical density range.

It is Agrément approved and designed to alleviate the lateral force of ground movement on foundations. Claymaster does not compress significantly until loads exceed 20kN/m2.
A load of 40kN/m2 is needed to produce 50% compression. Consequently its use is not recommended under ground floor slabs.

Claymaster is totally unaffected by water, and like Cellcore it can be used on sites where the
foundations are below the water table. It is available in a range of thicknesses, that will
compress to accommodate selected levels of predicted ground movement.


Claymaster is produced in a standard size panel 2400mm long, by 1200mm wide, with thicknesses ranging from 50mm - 300mm. However, Cordek provide a made to measure
service on length and width, with special shapes like circular sections cut to order.

Selection of Claymaster
Lateral ground movement and void characteristics
Shrinkage Potential Predicted Lateral movement NHBC recommended void Claymaster thickness for 'equivalent void'
Low Zero Zero
Medium 25mm 50mm
High 35mm 75mm
*Very High 60mm 100mm
*This category is recognised by the BRE

Deep Trenchfill is a traditional type of house foundation and where necassry Claymaster is used to protect the sides agains ground movement.

Due to more conomic piling methods, disposal cost of excavated material and stricter Health & Safety regulations, its use is declining.