Clay plaster

With its quality of honest authenticity, clay is gaining popularity as a construction material. It is especially prized as a material in dry rooms, thanks to its property of moderating air humidity, ensuring a better microclimate for living.

For centuries, clay has been used to build homes and other structures, as well as a filler. Today thanks to its qualities, it is seeing increasing use in interior finishing.

Properties of clay

  • Clay is free of volatile organic compounds (methane, aldehydes, ketones and so on), non-toxic and antistatic. Thanks to the antistatic properties, clay walls don’t attract dust, which reduces the amount of airborne dust and less will be breathed in. Clay also has the ability to block high-frequency electromagnetic fields.

  • Clay has the ability to moderate relative air humidity. As clay is able to absorb excess moisture from the air and return it to the air when the air becomes dry, no clay interiors are ever too dry or too damp.

  • As a binder, clay does not solidify or harden, and thus it absorbs and draws moisture faster and better than any other construction material. Measurements taken over several years in Germany show that interiors with clay walls have a relative humidity of 50% varying only 5-10% (G. Minke, Building with Earth). The ideal air humidity for people is 50-60%. Under 40% causes dry skin and air passages while over 70% promotes mildew. Thanks to clay’s property of moderating air humidity, it ensures a good microclimate indoors, which is the main condition for a high-quality living environment.

  • Inhospitable for mould and mildew – as the pH of clay is 7-8.5 (neutral to mildly basic) and can conduct moisture well, clay surfaces check mould growth better. Mildew needs high air humidity (> 70%) and a more acidic pH (4.5-6).

  • Clay helps to conserve wood – as clay has a lower balance moisture level (0.4-6%) than wood (12%) moisture always passes from wood to clay, leaving the wood dry and thus keeping the wood from being damaged by fungal growth or insects. Insects need about 14-18% moisture, and fungi over 20% (G. Minke, Building with Earth).

  • Heat retaining – as a high-mass material, clay has good insulating properties and this it makes a suitable passive heat; it also balances the interior climate.

Clay plaster can be used for many different kinds of surfaces

  • reed board

  • wood (in this case, first cover the surface with reed mat or reed board)

  • brick

  • concrete

  • light concrete

  • cinder block

  • Aeroc

Rendering

It is advisable to apply three or more layers of plaster, making sure that none is more than 10 mm thick. Excessively thick layers of plaster and too rapid a set are the main reasons for cracking.

Finishing

The plaster gets its final appearance from various finishing methods and materials. The result is a distinctive, even unique interior. We choose the finishing method and possible materials based on the customer’s vision.

Clay plaster rendered surfaces must not be covered:

  • with latex, oil, alkyd or polymer paints

  • polymer plasters

  • cement plaster

Clay surfaces should not be exposed to water unless the surfaces were waterproofed in the final finishing phase.

The exterior surfaces must be covered with whitewash and the proper building structures used (projecting eaves, high socles, drainpipes, etc.).

Use of clay for different construction components

  1. Amorphous clay construction material

    1. Rammed earth

      • Floor

      • Bearing walls

      • Non-bearing walls

    2. Clay straw

      • Non-bearing walls

      • Rendering

      • Ceiling, roof

    3. Light clay

      • Non-bearing walls

      • Rendering

      • Ceiling, roof

    4. Loose clay

      • Floor

      • Ceiling, roof

    5. Loam mortar

      • Bearing walls

      • Non-bearing walls

  2. Moulded clay construction material

    1. Loam block

      • Bearing walls

      • Non -bearing walls

      • Ceiling, roof

      • Dry (mortarless) construction

    2. Loam panel

      • Bearing walls

      • Non-bearing walls

      • Ceiling, roof

      • Dry (mortarless) construction

 

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