Walls and ceilings can be plastered with a variety of different surface treatments according to individual expression and comfort. Thicker layers of plaster of 1.5 cm or more make the most of earth’s sorption properties and help improve the indoor climate by regulating humidity. Earth plasters can be categorised as follows:

Fine clay plasters are made of clay and fine aggregates. They are usually applied by hand, seldom with a machine, with a thickness of between 2 and 5 mm. Commercially produced fine clay plasters are available as dry mixtures. Here too it is usual to apply a final surface coat of paint.

Fine coloured clay plasters are made of specially selected clay and earth with distinctive colourings and mixed with fine aggregates. Pigments can also be used to colour the clay mixture. These are likewise typically applied manually rather than with a machine, with a thickness of between 2 and 5 mm. The surface colouring is such that no further treatment or painting is required.
 

Brushable clay plasters are a recent addition to the range of commercially available plaster products. These are in essence a coating material in which earth and clay contribute only partially to the final surface hardening. In contrast to coloured clay plasters, these plasters contain coarse additives.

An alternative approach to wet plastering is offered by earthen plaster boarding. Pre-manufactured medium-sized boards are stuck to the backing surface much like tiles using earth mortars or adhesives.

Important: Earthen plasters and renders are usually applied in two coats enabling a better surface treatment. Surfaces to be plastered must be free of rising damp and salt efflorescence, dry, firm and free of dust and loose particles. A roughened surface improves adhesion. Junctions between different surface materials should be covered with reinforcement mesh, reed-matting, jute or glass-yarn webbing to avoid movement cracks. Earth renders must be allowed to dry quickly to avoid temporary mould from forming. Artificial drying can help speed up the drying process.

Note: Professionally produced earth plasters and mortars have a stable and abrasion-resistant surface and are suitable for wall surfaces in domestic and similar situations. The consumer is advised to check and compare the different products on the market depending upon personal requirements.