CLAY HEAVE PROTECTION BOARD

Clay heave protection board known as a 'low density compressible side panel' such as Claymaster, Clayfill, Claylite or Heaveguard is a fill perimeter material used for vertical installation against the sides of ground beams, piled foundations and deep trench fill foundations (up to 2m deep) to prevent problems in foundations where the soil has a high clay content and is liable to heave. In other words, Claymster is a perimeter polystyrene used to wrap the outer face of foundation designed to alleviate the lateral force of ground movement on foundations.

Clay heave boards may come as alternative names: Clayshield, EPS, Expanded Polystyrene, Compressible Fill or lateral Clayfill. Anti-heave board is manufactured from EPS blocks using expansion moulding process and wire cutting technique. EPS is the perfect clay heave protection solution as it is water and rot resistant and will never lose its compressibility. It is rot proof, not affected by bacteria, mould or fungi and will not provide nutrient value for insects or vermin. Expanded Polystyrene clayshield does not lose any performance over time and will remain effective for the life of the building. Moreover, it is non-toxic, non-irritant and odourless, making it completely safe to handle.

CLAY HEAVE BOARD SIZES & COLOURS

Boards are coloured for easy identification on site and are available in 8 different thicknesses such as 50mm, 75mm, 100mm, 125mm, 150mm, 175mm, 200mm and 300mm. Panels are delivered either in size 2400mm x 1200mm (8' x 4') or 2400mm x 600mm (8' x 2').

Claymaster comes in colour Pink, Heaveguard  in Light Green, Clayfill is Orange and Claylite is Green. The required thickness of the board will vary depending on the potential ground movement and the allowable pressure limit of the foundation substrate.

All compressible polystyrenes do not compress significantly until loads exceed 20 kN/m2. A load of 40kN/m2 is needed to produce 50% compression of the product. Its special compressive breaking point and thermal resistance properties mean it is perfect for meeting the current regulations for foundation construction.

CLAY HEAVE PROTECTION BOARD MANUFACTURERS

Jablite® Claymaster –  50mm | 75mm | 100mm | 150mm | 200mm Coloured PINK
Cordek® Heaveguard –  50mm | 75mm | 100mm | 200mm | 300mm Coloured LIGHT GREEN (alternative product that replaces Claymaster)
Kay-Metzeler® Claylite –  50mm | 75mm | 100mm | 125mm | 175mm | 200mm | 300mm Coloured GREEN (alternative product that replaces Claymaster)
Stylite® Clayfill –  50mm | 100mm | 150mm | 200mm Coloured ORANGE (alternative product that replaces Claymaster)
Max-frank® Clayfill – 50mm | 75mm (alternative product that replaces Claymaster)

CLAY HEAVE BOARD PRICE

In terms of cost (price), you should expect to pay for a standard 50mm clay lateral heave protection board  £29.98. Next size up thickness, 75mm board, should cost not more than £34.50. Those thicknesses are currently the most commonly used in the UK. In terms of a brand, Jablite Claymaster and Cordek Heaveguard are the leaders in the ground protection field. 

WHAT IS GROUND HEAVE?

Heave occurs because the moisture increases in an active soil. At the molecular level, a negative pressure potential (suction) in the soil particles attracts water molecules to a tight bond around the surface of the soil particles. Because water is incompressible, the clay particles are forced apart, causing soil movement. Heave can occur from 3 main areas either as a result of potential volume change from expansive clay soil or from reconstituted slag which is a by-product of the mining industry or the freeze cycle.

The freeze cycle really is where we are looking at areas of permanently frozen strata that may thaw or freeze and it is that thawing and freezing cycle that is replicating what a clay soil does when it expands under heave. The Building Research Establishment estimates that in situations where there are trees on shrinkable clay soils, the surface movement can be up to 100mm.

WHEN IS CLAYMASTER SIDE HEAVE PROTECTION BOARDS REQUIRED?

Claymaster is generally required on the inside face of external ground beams. However, in ground beam and pile beam applications it can be used on both faces of the beam. The appropriate thickness the product required is determined by the predicted lateral movement. Typically the material will be placed against the face of the beam after striking of the formwork and prior to backfilling. Compressible fill must not be used where the depth of in situ concrete is greater than 600mm in ground beam construction. As the product is confided underneath concrete ground beams and placed at the vertical face of deep trench foundations and has suitable durability, maintenance is not required.

HOW DO I KNOW IF I HAVE GOT HEAVE?

You should undertake a site investigation. That can be done by either a specialist geotechnical site investigation company. That may be a standalone company or some of the larger structural consultancies that could be an in-house operation, one of the services that is provided by those particular people. The other way of actually finding out if we got heave is if we don't want to have a specialist geotechnical site investigation undertaken we can refer to historical information. That can be provided either by NHBC or local building control or perhaps even just simply consulting the geology map of the UK and understanding where expansive clay occurs. 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.

DETERMINATION OF CLAY SHIELD BOARD THICKNESS

It is important that the specified thickness of clay heave protection board required to resist the pressures exerted from the ground movement is correctly calculated. Below calculation breaks down the thickness of clay heave protection needed. The specified clay heave board thickness should be:
     

 T = 100 x (H/C) + 10 

T= Thickness Required
H= Predicted maximum ground movement
C= Compressive strain (%) under maximum pressure exerted on foundation

CLAY HEAVE PROTECTION BOARD INSTALLATION

Anti-heave product is designed to be installed by a competent general builder, or a contractor, experienced with this type of product.

As general, the clay heave protection board is laid closely butted on the prepared excavation, ensuring that the whole area of the ground beam is covered. Clay heave boards can be joined together with fixing pins. 

It can be cut on-site using a fine tooth saw or a hot wire cutter. Clay heave protection board should not come into contact with any PVC cables. This is to avoid plasticizer migration which causes PVC cables to become brittle and fragile.

Also, it is not recommended for use under ground floor slabs or pile caps. Small gaps between boards should be filled with polystyrene pieces or must be backfilled with a granular material. Where concrete piles protrude into the trench, boards should be cut to suit with a fine-toothed saw. The excavation must be founded below the movement zone of the clay and the board positioned in accordance with NHBC requirements, 500mm above the trench bottom.

Vertical faces of trench-fill foundations
Picture credit:https://www.kay-metzeler.com/uploads/2/5/0/5/25058929/bba_claylite_certificate_2013_07.22.13.pdf

near me

Realated articles:

160mm DUFAYLITE CLAYBOARD vs 160mm WHITEROCK HEAVE STOPPER

COST-EFFICIENT UK ANTI-HEAVE PROTECTION: TOP 3 NEAR YOU

HOW TO CUT POLYSTYRENE VOID FORMER

SELECTING RIGHT VOID FORMER

Collapsible void former installation guide

Claymaster installation guide

Void former thicknesses

Ground heave solutions 

Foundation heave problems. Heave Symptoms

Don't let your foundation fail

Understanding Dufaylite Honeycomb Claybord Void Former

Filcor 20 Price

Breaking down Filcor

Understanding HX Plus

Filcor lightweight structural fill

How to insulate under concrete floor. The ultimate guide