FAQ Guide

General FAQ

What is Leca® LWA?

Leca® Lightweight Aggregate (LWA) was first produced in Scandinavia in the 1930's for the production of lightweight blocks, it was soon discovered that the insulating properties of the material could be of benefit to failing highways and railways throughout Scandinavia and in 1958 following many years of testing Leca® LWA was accepted as a proprietary fill material in the Scandinavian countries.


The raw material selection and production of Leca® LWA is strictly controlled to ensure a uniform, high quality product that is structurally strong, stable, durable and inert in addition to being lightweight and insulating.  Today Leca® LWA is used in many applications such as Geotechnical Fill, Masonary Blocks, Horticultural Blends, Filtration and Bio-filtration.

How is Leca® LWA manufactured?

Leca® LWA ia a ceramic lightweight aggregate produced by expanding selected clays; glacial clays tend to contain most of the essential properties allowing expansion when heated to their optimum. Once treated, the excavated clay is passed through a rotary kiln and fired to a temperature of approximately 1150°C.  This process expands the material 4 to 5 times its original volume creating ceramic pellets with a cellular inner structure.

Will any measures be needed to protect the fill material from degrading under any circumstances?

It is necessary to separate the Leca® LWA from any surrounding material containing fines by use of a geotextile to prevent migration in to the open textured Leca® layer. Depending on the materials use and location, it is usual to cap the Leca® to protect the fill from contamination and growth.


Where loading is expected, the capping layer type and thickness is to be calculated to avoid point load and distribute the load adequately to prevent crushing and rutting.


During construction, in order to limit mechanical breakage which usually occurs in the top 75 - 100mm layer, it is best to compact using the deepest compaction layers possible - up to 1 metre.  This breakage though will not affect the performance of the Leca® LWA but may increase the reduction in volume from 8-12% to as much as 15-20% if thinner layers are installed, narrow tracked compaction vehicles used or the number of recommended passes exceeded.


Leca® LWA is ceramic (fired clay) which is not known to degrade due to water being apparent or time.


Please contact us  should you need further information or clarification.

What is the steepest slope that can reasonably be achieved for the embankments given that they may be up to 11m high?

The angle of friction given for Leca® LWA 10-20mm is 35°-39° (average 37°). A 1:2 slope is suggested however, other methods are available should the slope face need to be increased. For more information and guidance please contact us.

Will the material have any adverse effects or environmental issues regarding flora & fauna?

Leca® is not known to harm flora and fauna and is in fact used by many horticulture applications such as within growers green houses, green roofs, sports pitches, flower beds etc. and is accepted by the British Orchid Grower Association. When mixed with soil, Leca® will increase aeration to roots and moisture retention within the pellet can keep the soils moist for extended periods during dry weather conditions. For more information and advice, please contact us.

Are there any issues with destabilisation of embankments by animals?

We are not aware of any embankment destabilisations due to animals and would expect Leca® to prove difficult for the animals to burrow. We would recommend similar consideration be used as that when using traditional fill.

Will roots of trees etc., potentially destabilise the embankments?

We are not aware of any embankment destabilisations due to tree roots but would recommend similar consideration is used as that when using traditional fill.

As embankments are in possible flood risk areas, what are the issues associated with floatation/degradation of the materials or might there be any other issues caused by the embankment location?

Leca® LWA is a stable ceramic pellet hence no degradation has been experienced or is expected to the material.  The compacted fill allows the water to rise and fill all of the voids between the pellets and then quickly drain away when water levels drop. The individual pellets will absorb a percentage of the water, increasing over time with a maximum of approx. 85% of material weight with long term saturation.  The pellets will dry over time once the water has subsided.  For more information and advice please contact us.


Where trenches etc., have to be dug in the material, what issues are there & how have they been overcome elsewhere?

As with all trenches; adequate trench support should be used when digging beyond maximum unsupported depth criteria or if the conditions are deemed unstable. Leca® LWA pellets have open pores on the surface which helps in achieving the friction angle of 37°


When compacted, the pellets interlock and will remain that way when compacted and capped, for this reason, the Leca® LWA should stand without total ravelling for a limited period i.e. to allow the installation of drainage, ducting etc.


However, we would recommend that relevant Shoring equipment is used in accordance with Health and Safety Guidelines. For more information or advice please contact us.

Safety fencing will be required on the embankments, will the material provide adequate support for normal driven posts or will another foundation system be required?

If it is a crash barrier, it would probably be best to increase the depth of the capping layer in that area in where posts are planned.  However, if it is simply a safety fencing or perimeter fence or sign post, etc., it is usual that a minimum 250/300mm diameter sleeve is initially positioned in the Leca® LWA, ready to accept the posts which are then concreted and secured into position.

The embankments may be landscaped, potentially with trees. How will the material support & nourish the planting that may be required?

If the material is needed as a support to the planting of mature trees, then it may be advised to insert a former into the area where the tree roots are to be planted and when planting is to take place mix the soil with Leca® LWA, remove the former and plant as normal; however if the plants are young as they are in most cases such as this then planting directly into the topsoil capping layer will suffice.

Might the material restrict growth of the possible landscape planting on the embankments?

Leca® LWA is used as a growing medium so it will actually promote growth. In this type of application, it is likely and there should be a geotextile and topsoil between the Leca® LWA and the vegetation during planting. However, after a period of time the roots will find their way through the woven geotextile and work with the Leca® LWA where they will receive air and moisture trapped naturally within the material. For more information and advice please contact us.

What is the carbon footprint of providing the material - especially in comparison to other locally sourced standard bulk fill materials?

As you would expect, as Leca® Lightweight Aggregate (LWA) is produced in a kiln the carbon footprint effect appears high however, our production team are continually looking for ways in which to reduce and offset these effects by using for example, materials that would normally be sent to landfill for use in the burning to heat the kilns which in turn is re-directed as a renewable energy for the factory and offices. 


During transportation, we keep the CO2 emissions reasonably low by shipping the Leca® LWA in large volumes.  Once the material reaches the UK port, it is stored at the port until it is required by the customer, so no increased CO2 emissions through double handling.  When required by the customer, we transport as much material as possible per vehicle using walking floor trucks which in the dry June of 2011, one delivery was calculated at 102m³. Walking floors can carry in excess of 70m3 of Leca® LWA, up to 8 times more volume than that of traditional aggregate and soils, hence less vehicle journeys!


When being installed in a typical application, the overall energy exerted during the placement and compaction of the Leca® LWA is considerably reduced due to the deeper compaction layers, the type of compaction equipment used, less volume reduction during compaction and the fewer passes necessary to achieve optimum compaction.
Leca® LWA is an inert material that can be used and re-used on site and there is no need for disposal of excess to landfill.

Are there any issues in placing and compacting the materials?

Leca® Lightweight Aggregate (LWA) is much faster and easier to place than traditional fills due to its light weight, rounded nature and installation layers of up to 1 metre in depth which will help save program time and cost. However it is due to its rounded nature, the construction process needs consideration as this material cannot be driven over by wheeled vehicles until capped. It is recommended that wide tracked vehicles are used to place and compact Leca® LWA

During installation, in order to limit mechanical breakage which usually occurs in the top 75 -100mm layer due to the point load of the compacting vehicle tracks on the pellet and vehicle turning, it is best to compact using the deepest compaction layers possible of up to 1 metre depth and ensure the recommended compaction passes are not exceeded to avoid over compaction. This breakage will not affect the performance of the Leca® LWA but may increase the compaction loss from 8-12% volume to as much as 15-20%.  Where thinners layers of Leca® LWA are required i.e. 150 - 600mm, the compaction equipment should be limited to a vibrating plate compactor if feasible. In difficult to access areas, Leca® LWA can be pneumatically installed using the Leca® blowing vehicle.

For more information and advice please contact us.

Are the materials inert or subject to degradation by fuel spillage, acids, fire etc?

Leca® Lightweight Aggregate (LWA) is clay made inert through the firing process and is not subject to degradation, from chemical or acid spillage. Temperatures would have to exceed 1200°C before any concern of the effects to the Leca® lightweight aggregate.

Are materials subject to creep?

Data shows less than 3% creep in 100 year test which is as good, if not better than crushed rock.

Are there any particular storage issues such as dust, moisture loss etc., that could affect stockpiling (additional costs for protection)?

Storage of Leca® Lightweight Aggregate (LWA) should be on clean hard standing or a geotextile covered area to avoid the migration of sub-soils or localised stone/rock being dragged into the material.

Inclement weather will not adversely affect Leca® LWA though moisture will increase the material density which will fluctuate given the level of moisture obtained or released.

If storing in dry weather conditions, it may be advisable to dampen the Leca® LWA to avoid airborne dust where necessary

It is advisable to store Leca® LWA away from an area likely to flood. However if this is not possible, bund the storage area to prevent floatation.

Are geotextiles required for side slope stabilisation?

Geotextiles are used primarily to prevent the migration of fines into the Leca® Lightweight Aggregate (LWA) fill and not for stabilisation purposes.

Should increased stabilisation be required or the side slope increased to in excess of 1:2, there are a variety of methods used which do include Geotextiles and geogrids however, please contact us for further information.

Is a drainage layer required?

Leca® Lightweight Aggregate (LWA) is a free draining material and regularly used as drainage media. No additional drainage layer is required but in an area subject to flooding, it is good practice to install weep pipes through the capping within the base of the Leca® LWA fill to allow the water to drain out when waters subside as the capping layer may act as a tanking.

Are there any requirements for issues with wick drains?

Wick drain requirement is identified during design consideration and usually not required when installing Leca® Lightweight Aggregate (LWA). Wick drains have been used in conjunction with the use of this material before now but it is advisable to consider the self-draining properties of Leca® LWA before designing in wick drains which may not be required.

Are there any durability issues?

Long term durability under dynamic load compaction tests shows Leca® Lightweight Aggregate (LWA) to perform better with less long term crushing, than stone.

What is the cost per m3?

The cost of delivering Leca® Lightweight Aggregate (LWA) will vary depending on location, site conditions and any special requirements that may need to be considered in terms of delivery. Please contact us to discuss your requirements and obtain cost indication or quotation.

Where are the materials for Leca® sourced/ produced?

We have kilns located across Europe but for the UK, we import primarily from our Danish, Portuguese and Norwegian kilns. Our stock is located in the ports of Goole, Garston, Newport and Kings Lynn however, depending on volume required, we can ship to a port better located to suit your needs.

For more information please contact us.