Clay shrinks during periods of drought and expands again after heavy rainfall. Foundations built on shrinkable clays can normally be affected to a depth of 1m but, where there are trees and hedges, the depth affected increases.
The Building Research Establishment estimates that in situations where there are trees on shrinkable clay soils, the surface movement can be up to 100mm.
Clay heave can impose both lateral and vertical pressures on foundations, often resulting in cracking and expensive structural damage.
While piled foundations offer more protection than conventional trench fill, both types still remain highly vulnerable to clay heave, shrinkage or soil movement.
In latter years it has become standard practice to protect building foundations with compressible fill such as Claylite which is purposely designed to absorb natural contractions and expansions within clay and other types of soil.
Claylite is a low density expanded polystyrene board produced in a light green colour for easy identification and developed to protect foundations of new buildings from clay heave, shrinkage or soil movement in trench systems up to 2.5m deep. This depth can be increased by staggered concrete pours.
Claylite EPS compressible material is used regularly on a wide range of constructions for all types of buildings and has rapidly been accepted as the best solution to movement caused by clay heave, shrinkage or soil movement.
In ground beam and pile and beam applications Claylite can be used on both faces of the beam.
Four types are produced:
Claylite for standard applications with ground beams and in even sided trenches.
Claylite Super for extra strength in uneven sided trenches.
Claylite Castellated for fitting under lightweight ground beams.
Claylite Super Castellated gives added strength and stability over Claylite Castellated.