What is expanded clay? - Properties, uses and sources of purchase

What is expanded clay? - Properties, uses and sources of purchase

the essentials in brief

  • Expanded clay (€ 17.50 at Amazon *) is granulated, fired clay that expands many times over at 1200 ° Celsius to form small balls.
  • Expanded clay is germ-free, rot-proof, frost-proof, dimensionally stable, fire-proof and insulating. Expanded clay balls have a closed-pore core with a porous surface so that water is absorbed and drained, but not absorbed.
  • Expanded clay is to be used as a natural product for garden and plant care as well as in ecological house construction.

What is expanded clay?


The starting material for expanded clay is low-lime clay with organic components and without chemical additives. For the production of extracted clay is ground and burned in a furnace at 1200 ° Celsius. During this process, the organic components burn in the clay balls, which expand many times over. The result is a light and round shaped granulate with the aptly named expanded clay or clay granulate. Expanded clay is characterized by the following properties:

  • germ-free : does not mold
  • neutral : no influence on the pH value
  • structurally stable : pressure-resistant, prevents compaction and waterlogging in soil
  • weather-resistant : can be used outdoors and indoors
  • rotproof : inorganic, does not decompose
  • fireproof : non-flammable
  • insulating : good sound insulation, medium thermal insulation (0.10-0.16 W / mK)
  • environmentally friendly : does not contain any chemical additives

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The firing process creates expanded clay balls with a closed-pore core that is surrounded by a sintered, fine-grained surface. This process has a decisive influence on the behavior in water. Expanded clay does absorb moisture in its shell. However, the closed-pore core prevents water from being absorbed.

Expanded clay was invented at the beginning of the 20th century in the USA by S. Hayde, to which the American name Haydite refers. The internationally popular brand name for expanded clay is Leca, as the abbreviation for lightweight expanded clay aggregates (slightly expanded clay aggregate). Keramsite is a rarer name.

What can you do with expanded clay? - overview

Sensitized environmental awareness has brought expanded clay into focus for natural garden and plant care. In ecological house construction, the niche product is at the beginning of a steep career as a natural building material. In view of the impressive properties of the clay granulate, the following possible uses have emerged so far:

gardenPlant careHouse building
Soil improvementDrainage materialBuilding material
Raised bed drainage substrateHydroponicsinsulation
Tree substrateSubstrate componentBricks
Light gravelIncrease in humiditySound insulation fill
Winter gritMulch

Are you consulting this guide because you want to use expanded clay as an innovative building material? Then we recommend reading numerous specialist articles on Hausjournal.net. Here you can read how you can use the special advantages of expanded clay, for example for thermal insulation as a fill or as a lightweight aggregate for bricks or cement. The possible uses are examined in detail, including their advantages and disadvantages.


Expanded clay optimizes green roofs


In ecological house construction, expanded clay perfects the substrate for green roofs. On the roof, the substrate acts as a rooting layer for the vegetation and drainage for the purpose of draining water. For this purpose, nutritious topsoil enriched with expanded clay is broken. For perfect functionality, the topsoil proportion should be reduced from top to bottom in order to optimize the drainage effect. Furthermore, it is recommended to lean the heavily clay-emphasized substrate with fine-grain sand for vital growth of the special green roof plants.

Expanded clay use in the garden - tips & tricks

Hobby gardeners who are close to nature have discovered expanded clay as the ideal problem solver for a variety of tasks. Thanks to the airy, light, water-conducting clay balls, the framework conditions for plant growth can be improved in harmony with nature. What the above table indicates in terms of keywords will be examined in more detail in the following sections.

Soil improvement

Garden soil with a high proportion of loam and clay is prone to severe compaction. Because the rainwater does not run off or runs off slowly, damaging waterlogging occurs. Vegetable plants, flowers, shrubs and woody plants suffer from permanently wet roots and die. By mixing clay granules with heavy garden soil, you can solve the problem. How to improve the soil with expanded clay:

  1. Dig bed soil two deep into a spade (optional seven)
  2. Work in 3 liters of ripe compost soil per m² of bed area
  3. Mix in a handful of expanded clay per liter of compost
  4. Smooth out the improved garden soil with the rake

Please use expanded clay with a medium grain size of 4 to 10 mm to improve the soil. Finer grain sizes harbor the risk of silting up and thus cancel out the desired loosening and aeration effect in the soil.

Drainage substrate in the raised bed


Filling a raised bed properly takes a good deal of expertise and even more time. Understandably, hobby gardeners look specifically for an uncomplicated solution. A clever move is the use of a ready-made raised bed filler. The lead company here is Liapor with a high-quality special product based on expanded clay. Thats how it works:

  1. Cover the floor in the raised bed with rabbit wire against voles
  2. Put a 30 to 50 cm high layer of raised bed filler on top
  3. cover with a drainage fleece
  4. Fill in ripe, sieved compost soil as a plant layer 15 to 25 cm high

With the Liapor raised bed filler you use a natural, balanced base and drainage material that keeps your plants back free. Waterlogging, root rot or mold have little chance of impairing vital growth and rich crop yields. Thanks to the low weight of expanded clay, back-friendly gardening begins with the filling of the raised bed.

Tree substrate

Trees go through a delicate phase in the first two years. In order for underground and surface growth to run smoothly, the best possible framework conditions in the soil are essential. With expanded clay as an additive in the tree substrate, you can effectively prevent negative influences from waterlogging on the day of planting. The high firing temperature in the manufacturing process makes expanded clay balls extremely durable. Extreme loads caused by frequent alternation between freezing and thawing weather do not prevent clay granules from continuously guaranteeing the best water permeability and permanent soil aeration.

Light gravel

Expanded clay is very popular in creative gardening and landscaping. In contrast to clay balls, broken expanded clay fragments interlock when they are applied to the substrate. Furthermore, expanded clay as lightweight chippings is frost-resistant, rot-proof and moisture-regulating. The granulate only absorbs moisture for a short time on the porous surface. Without swelling, excess water is quickly conveyed into the deeper soil layers for an effective drainage effect. Thanks to a dry bulk density of around 0.5 t / m³, expanded clay is a real lightweight compared to gravel and conventional chippings.

These properties make broken expanded clay the ideal substructure for patios, garden paths and seating. For this purpose, expanded clay granulate with a fine grain size is applied as a fill about 4 centimeters high.

Winter grit

Broken expanded clay is recommended for use as an environmentally friendly winter grit to prevent the risk of slipping. This variant reduces the purchase price by up to 50 percent. Furthermore, the sharp-edged clay granules are much better suited than small balls to sprinkle icy garden paths and driveways so that they do not slip.

Expanded clay in plant care - instructions for beginners

Once amateur gardeners have come to appreciate its advantages, they no longer want to do without expanded clay in plant care. The following brief instructions explain how you can elicit the benefits of this natural product:



As a drainage, expanded clay deserves the predicate excellent. Because the fired clay balls do not soak up the water, but pass it on, waterlogging in boxes, buckets and flower pots is a thing of the past. Fill in a layer of expanded clay about 5 centimeters high over the openings in the floor, which you cover beforehand with a pottery shard. Excess irrigation and rainwater can now drain away quickly. Use a drainage fleece so that no crumbs of earth cheat between the expanded clay balls. This is an air and water permeable fabric that you spread between the substrate and the drainage system.



The good clay for magnificent houseplants comes in the form of expanded clay. By placing your soil-bound plants in expanded clay, the guesswork of getting the right water and nutrient supply a thing of the past. If sophisticated orchids reside in expanded clay, the rainforest beauties indulge in an opulent frenzy of flowers. The key word for this motivating, horticultural sense of achievement is hydroponics. Using this principle, you can also plant large pots with expanded clay. You need a waterproof planter with a special inner pot, expanded clay, water level indicator and nutrient solution. How to proceed correctly step by step:

  1. Soak expanded clay for 12 to 24 hours
  2. Pot the plant and shake off the soil
  3. Rinse the last remaining substrate from the root ball
  4. Place the bare plant roots in the middle of the special inner pot
  5. Position the water level indicator in the inner pot so that it is easy to read
  6. Pour in expanded clay
  7. Push the inner pot gently onto the table to ensure that the clay balls are evenly distributed
  8. Place the pot in the watertight planter

For the first watering, fill in water at room temperature up to level 1 on the water level indicator. Expanded clay directs the water to the roots with the help of capillary force. In the future you can read on the display when you should water the plant again. Because hydroponic plants cannot live on water alone, a special nutrient solution ensures the supply of all important nutrients.

Substrate component

The joy of inexpensive potting soil does not last long, because compacted substrate in pots and balcony boxes constricts the air from plant roots. This shortcoming does not mean that you will have to forego special offers in the garden center or hardware store in the future. As soon as you mix a little expanded clay with the soil, the substrate is airy and loose. Fine clay granules with a grain size of 1 to 4 mm are well suited. Because expanded clay is structurally stable and pressure-resistant, the substrate cannot collapse even after a long period of time. Plants and nature are completely happy when you upgrade peat-free potting soil with expanded clay.


Increase in humidity

Right at the start of the heating season, tropical indoor plants rebel against the dry indoor air. Almost all exotic potted flowers depend on a humidity of more than 50 percent. If the value falls below this level, growth depression, leaf and flower fall are inevitable. This is where expanded clay comes into play to regulate the room air without mechanical humidifiers. It's that easy:

  1. Fill the saucer of the pot or bucket with expanded clay
  2. Place the vessel on the expanded clay
  3. Pour water into the coaster

The water evaporates over the spherical, rough surface and rises as steam. This creates a microclimate in the immediate vicinity of the plant with increased humidity.


Weed control is a tiresome topic when it comes to caring for majestic potted plants and large flower boxes (€ 13.18 at Amazon *). Primarily woody plants gradually shed the base. The exposed surface of the earth causes weeds that spoil the well-tended appearance. Annoying weeding is the annoying consequence. It doesn't have to go that far if the plants are covered with a mulch layer made of expanded clay. With a layer height of about 2 centimeters, clay granules suppress the growth of weeds without hindering the water and nutrient supply.


Contrary to popular belief, expanded clay does not act as a water reservoir. As a result, clay granules do not extend the watering intervals when used as an aggregate in potting soil. The test to the example provides the proof. Put a handful of expanded clay in a glass of water. The spheres still float on the water surface after hours and do not soak up completely.

Buy expanded clay - shopping sources with price comparison


Expanded clay had a niche existence for a long time and was difficult to find in stores. Since word of the environmentally friendly properties got around, more and more hardware stores are adding the product to their range. We looked around the market to see what is on offer and the price structure. The following overview lists purchasing sources with price comparison:

providersPrice 2-2.5 lPrice 5 l10 l50 l
bauhaus2.95 EUREUR 10.95EUR 21.90no offers
Obi2.69 EUR4.99 EUR5.99 EUR18.99 EUR
Toom4.49 EUR6.49 EUR9.49 EURno offers
Hornbach2.95 EUR6.95 EUR9.99 EUR (15 l)no offers

If you want to buy expanded clay cheaply in a 50 l bag, you will rarely find it at well-known hardware stores. Here the offers usually end at 10 liters. Larger containers can be found on Amazon from 21.90 euros per 50 l for fine, medium or coarse grains. Hornbach is an exemplary supplier for hobby gardeners with a high demand for expanded clay. Here you can get a pallet with 1,260 liters (42 x 30 l) at a price of 605 euros with free shipping.

Please note that this price comparison is a snapshot that does not claim to be representative topicality. As with all products for the garden, plant care and house building, supply and demand determine the price.

Bargain hunters buy expanded clay in specialist shops

If hobby gardeners want to buy more expanded clay cheaply, the specialist trade comes into focus. Special companies for expanded clay fill as a building material usually offer suitable products for garden and plant care. The lead company is Liapor with the brand “Liadrain”, a plant-compatible expanded clay as a substrate component, for balcony and terrace greening as well as for filling raised beds. In Liapor-shop.de you can purchase a 50-liter sack for an inexpensive EUR 9.58 plus shipping costs.


Seramis is not expanded clay


A widespread lack of information about clay granules causes fatal failures in plant care. Many carpenters are mistaken that Seramis and expanded clay are identical. In fact, there is a major difference between the two materials. Seramis plant granules contain clay balls that have been subjected to a special process to increase the pore volume. As a result, the globules soak up water like a sponge. This high water retention is advantageous for plants that are in the ground, but unsuitable for hydroponics. In contrast, expanded clay does not store moisture, but operates with ideal water and air flow, which is vital for all hydroponic plants. As a result, Seramis plant granulate is not an alternative to expanded clay, but scores with other advantages.

Expanded clay reduces potting soil consumption

The most beautiful bedding and balcony flowers are dependent on a special substrate. To ensure that geraniums, petunias or azaleas bloom lavishly, amateur gardeners grind their teeth deeply into their pockets to buy high-quality branded products. With expanded clay, you put the brakes on consumption and costs. The one-time investment in an adequate supply is worthwhile, because expanded clay can be used again and again and does not lose its weight even after many years. This is how the horticultural trick works:

  1. Cover the floor openings with curved pottery shards
  2. Fill the bucket, pot or flower box (€ 13.18 at Amazon *) halfway up with expanded clay (fine to medium grain size)
  3. Cover the expanded clay layer with drainage fleece
  4. Fill in special potting soil and plant

Instead of drainage fleece, you can use worn-out nylon stockings, which also reduces costs. Fill each stocking with expanded clay and knot the top end. In this way, the clay granulate is spared dirt from the substrate, and can be easily lifted out of the planter at the end of the season and reused the next year.

frequently asked Questions

Is expanded clay poisonous?

Expanded clay is a purely natural product without chemical additives. The manufacturing process is limited to the crushing and heating of clay. For this reason, you are holding a completely harmless product in your hands with expanded clay, which fulfills a wide range of tasks in natural gardens and environmentally friendly house building.

Is there an alternative to expanded clay?


Perlite is extracted from obsidian, a volcanic rock glass. The natural material goes through a similar manufacturing process as expanded clay and has similar properties and uses. The only outstanding difference is the color of the beads. Perlite is white to cream in color and is reminiscent of popcorn. In contrast, expanded clay balls are colored red-brown, light or dark brown. In direct price comparisons, Perlite scores with a price that is up to 50 percent lower than that of expanded clay.

In which grain sizes can expanded clay be bought?

Expanded clay with a fine grain size of 1 to 4 mm is suitable as a substrate supplement for indoor and balcony plants. Furthermore, fine-grained clay granules are used in house construction as a fill for thermal insulation or soundproofing. In a medium grain size of 4 to 10 mm, expanded clay is used for hydroponics, as drainage in plant vessels and for soil improvement. With a coarse grain size of 10 to 20 mm, expanded clay often functions as a building material in ecological house construction. In addition, coarse-grained clay granules are useful as drainage for large container plants.

Can the advantages of expanded clay be used for a beautiful lawn on heavy clay soil?

If you are laying out a new lawn on heavy clay soil, expanded clay as an aggregate provides valuable protection against waterlogging. For this purpose, work a layer of 5 to 10 centimeters of expanded clay into the earth when you create the rough subgrade. You can rehabilitate old, mossy lawns with expanded clay and breathe new life into it. You can do this with narrow slots 3 centimeters wide and 5 centimeters deep, which you cut into the lawn every 60 centimeters. Then fill the small furrows with fine-grain expanded clay, sprinkle a mix of compost and sand over them and roll the lawn.

Is expanded clay suitable for growing young plants in hydroponics?

In fact, you can put young hydroponic plants in expanded clay from day one. Use a grain size of 1 to 4 mm so that the delicate roots quickly take hold. The clay granulate is thoroughly watered before it is used for the first time. Then fill the seed pot halfway with expanded clay. Place the young plant on the substrate, distribute the existing roots evenly and fill in the remaining clay granules. Now you can put the pot in a watertight container and pour it down to the minimum level. It is important to note that there must be no soil residue on the plant.

Can you use expanded clay as a filter medium for the garden kingdom?

The use of expanded clay as a filter medium is a matter of controversy among experienced pond owners. The porous surface of the clay balls is seen as critical. This is where bacteria, algae and debris build up over time, which can be detrimental to the health of fish. For a safe use in the pond filter, it should be ensured that expanded clay is regularly and thoroughly cleaned of deposits.

In what proportions should expanded clay be mixed with earth for optimal growth?

If you mix expanded clay with earth in a ratio of 1: 9, you will effectively prevent stunted growth. With this mixing ratio you give the soil a permanent loosening and oxygen supply. A higher proportion of expanded clay makes the soil too permeable, which is just as unfavorable for the plants as a structure that is too firm.

What is a drainage fleece?

A drainage fleece has the task of preventing the mixing of two different soil layers. It is a special fabric that is permeable to water and air. In combination with expanded clay in plant care, the drainage fleece prevents soil from settling between the clay balls. If you use clay granulate as light gravel in the garden, a drainage fleece also takes on the role of weed fleece.


As an environmentally friendly natural material, you can dispose of expanded clay in the organic waste bin or on the compost. In view of its many advantages, it is advisable to recycle valuable clay granulate, comparable to lava granulate. Simply rinse with clear water and the expanded clay is in top form for another use.