Void Formers

Void Former is a lightweight material in structural concrete in foundations, beam and slabs to fill structurally non-working areas and against clay heave. They are strong enough to support the weight of wet concrete as well as steel reinforcements. They come in either full form or in honeycombed form. 

Heave is the upward movement of an underlying supporting soil stratum due to the addition of water to an unsaturated expansive soil. When moisture is added to the soil, expansion occurs within the structure of the soil, and the corresponding area of the foundation moves upward. Heave most commonly occurs within clayey soils with an available moisture source.


Void spaces (gaps) are designed to provide an intended buffer zone or clearance between expansive soils and a concrete foundation in order that heave can occur without imposing detrimental uplift pressures to the foundation. Such voids are filled with expanded polystyrene compressible-fill material and/or specialised honeycomb materials. While the expanded polystyrene would compress and uncompress taking away the soil heave stress from the foundation and the foundation slab, the proprietary honeycomb system is a collapsible system, which would leave space under the foundation slab, after the honeycomb is bio-degraded.  The honeycomb system is used usually under foundation slabs. Void formers under the grade beams will typically be required if the uplift forces from the soil are greater than the dead load plus sustained live load of the foundation and superstructure.

Advantages

  • A foundation slab with void space below allows expansive soils to swell into the void space, thereby reducing the risk of foundation heave.
  • Foundation slabs that are elevated above the surrounding grade are less affected by surface water prior to concrete placement.
  • Allows to build on sites with inadequately compacted, untested soil or other soil conditions that may not be suitable to support the construction of grade-supported foundations.
Disadvantages

  • Creates a path for water to migrate below the slab, particularly when the bottom of the void space is near or below adjacent grade. 
  • Usually increases cost of the design and construction.
  • Concrete may enter the honeycomb form or the expanded polystyrene during placement, if any stakes are driven through them, or any space left between them.
Expanded polystyrene (EPS) is recognized and accepted as the lightweight fill alternative to soil and is increasingly used in commercial and residential applications. Given EPS' low weight, strength, and ease of use, it is used to solve construction challenges in following applications:
  • Lightweight structural void fill,
  • Lateral load reduction on structures,
  • Lateral and dead load reductions over buried utilities,
  • Soft soil remediation,
  • Slope stabilization
Benefits of using compressible EPS fill materials as an alternative to traditional soil fill.
  • Can be used where the use of larger mechanical equipment may not be feasible.
  • Project construction time is reduced.
  • Can be installed during any type of weather or site conditions.
  • Project construction time is reduced as it is lightweight.
  • Concrete, soil or any other material can be placed directly on EPS, eliminating formwork.


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50mm Claylite - Protection Against Soil Movement

50mm Claylite - Protection Against Soil Movement

1200x2400 - 2.88m2  show quantity discountsDelivery Time: 2 - 3 days

£20.82 (£24.98 inc VAT)

£7.23/m2 (£8.68/m2 inc VAT)

show quantity discounts

50mm Claylite is a low density expanded polystyrene compressible-fill material which can be used to reduce the pressure exerted on reinforced concrete ground beams or on the vertical face of concrete foundations, caused by the expansions of clay soils (clay heave) during the life of the st..

£20.82 (£24.98 inc VAT)

£7.23/m2 (£8.68/m2 inc VAT)

show quantity discounts
= m2
other thicknesses
50mm Claymaster

50mm Claymaster

2400x1200mm - 2.88m2  show quantity discountsDelivery Time: 2 - 3 days

£20.82 (£24.98 inc VAT)

£7.23/m2 (£8.68/m2 inc VAT)

show quantity discounts

50mm Claymaster is an EPS compressible-fill material which can be used to prevent potential problems in foundations due to moisture movement in soils which contain a large proportion of mineral particles below 0.002mm (clay heave). The material can be used as permanent shuttering for cast in-situ re..

£20.82 (£24.98 inc VAT)

£7.23/m2 (£8.68/m2 inc VAT)

show quantity discounts
= m2
other thicknesses
60mm Dufaylite Commercial Clayboard Void Former (pack of 33)

60mm Dufaylite Commercial Clayboard Void Former (pack of 33)

1000x2440mm - 80.52m2  Delivery Time: 3 - 7 days

£1,512.37 (£1,814.84 inc VAT)

£18.78/m2 (£22.54/m2 inc VAT)

60mm Dufaylite Commercial Clayboard Void Former is a lightweight board available in four different thicknesses, and especially applicable to large scale, commercial projects. It is made from extremely environmentally friendly components, lowering the carbon footprint of the building, but also provid..

£1,512.37 (£1,814.84 inc VAT)

£18.78/m2 (£22.54/m2 inc VAT)

= m2
other thicknesses
60mm Dufaylite Residential Clayboard Void Former (pack of 33)

60mm Dufaylite Residential Clayboard Void Former (pack of 33)

1000x2440mm - 80.52m2  Delivery Time: 3 - 7 days

£1,289.19 (£1,547.03 inc VAT)

£16.01/m2 (£19.21/m2 inc VAT)

60mm Dufaylite Residential Clayboard Void Former is a specially designed board consisting of a lightweight, eco-friendly and biodegradable core covered with polypropylene facings. The product is designed to prevent the common problem of expansion and shrinkage of clay soil when it is ..

£1,289.19 (£1,547.03 inc VAT)

£16.01/m2 (£19.21/m2 inc VAT)

= m2
other thicknesses
Filcor - Expanded Polystyrene (EPS) Structural Fill Material

Filcor - Expanded Polystyrene (EPS) Structural Fill Material

Filcor EPS  Delivery Time: 3 - 5 days

Filcor EPS is an Expanded Polystyrene lightweight structural fill alternative to more traditional fill materials or as a lightweight void former in structural concrete. The standard (and  the maximum) sheet or block size is 2400mm long x 1200mm wide x required thickness. The thicknesses fr..

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