Vermiculite Applications Floor Screeds

Vermiculite concrete can be laid over a wide range of sub-bases to provide an insulated and resilient floor. Its lightweight properties are of particular importance when used over suspended floors or for infill to accommodate different levels. It may be used to advantage where fire resistance is important.

Recommended thickness

For general applications a thickness of 80 - 150mm provides a satisfactory base, this may be reduced to 30mm for levelling purposes. Where the only requirement is to achieve minimum thermal insulation standards, thickness will vary with the shape, size and type of building. Based on a thermal conductivity of 0.12 W/mk, the table below shows the minimum thickness of screed necessary to achieve a U value of 0.45 W/m2k.

Length of Building (m)	Width of Building (m)	Thickness of vermiculite screed (mm)
Length of Building (m)	Width of Building (m)	Detached	Semi-detached End-terrace	Mid-terrace
Up to 10	Up to 10	165	129	83
10-15	Up to 10	129	108	*
	10-15	80	*
15-20	Up to 15	115	100
	15-20	41	*
Above 20	15-20	108	96
	Above 20	*	*

Protective Topping

With most lightweight concrete screeds it is necessary to provide a protection of the Vermiculite screed with a dense cement:sand topping. This distributes the floor loadings and prevents abrasion and other damage. There are two seperate methods of applying this topping.

1. Monolithically bonded topping

Within about an hour, an area of the Vermiculite screed is laid, a cement grout is brushed into the surface and the cement:sand topping immediately applied. Recommended thickness 20mm.

2. Unbonded topping

The vermiculite screed is laid and allowed to harden. The cement:sand screed is applied over the Vermiculite screed making no attempt to bond the layers. Recommended thickness 65mm.

Please note: Protective toppings with thicknesses of between approximately 25 and 55mm are likely to be unsatisfactory due to the difference in shrinkage of the materials.