Clay plaster

Clay plaster MINERAL 20

Single- or multi-layered basecoat and topcoat plaster for indoor use. Mineral clay plaster is a basecoat and topcoat plaster all in one. It contains angular fractured sand to ensure strength. After application, the mortar contracts quite quickly and can be worked with again after a short period. If used as a basecoat plaster, it is suitable for all coarse and fi ne CLAYTEC clay topcoatplasters, e.g. YOSIMA. If used as a rough or even smooth topcoat with a mineral, straw-free surface texture, it can be painted with the CLAYFIX clay paint system.

Type of clay plaster mortar
Clay plaster mortar for use as plastering mortar. Earth-moist.

Single or multi-layered basecoat and topcoat plaster for indoor use. Manual or machine plastering on masonry, solid building components, reed matting etc.

Natural building clay up to 5 mm, mixed-grain washed or crushed sand 0-2.8 mm.
Grain group: oversize grain according to DIN 0/4, < 5 mm.

Country of origin Germany

Material properties
Drying shrinkage 2.0%. Strength class S II. Bending tensile strength 1.0 N/mm2. Compressive strength 3.0 N/mm2.
Adhesive strength 0.20 N/mm2. Abrasion 0.2 g. Gross density class 2.0. Thermal conductivity 1.1 W/m∙K. μ-value 5/10. Vapour adsorption class WS III.
Building material class A1.

Supply form, coverage
Earth-moistened 05.030 in 1 t Big Bags (yields 500 l plaster mortar, 50 m2 area at thickness = 1.0 cm)
Earth-moistened 05.230 in 0.5 t big bags (yields 250 l plaster mortar, 25 m2 area at thickness = 1.0 cm)
Dry 05.032 in 1.0 t Big Bags (yields 540 l plaster mortar, 54 m2 area at thickness = 1.0 cm)
Dry 10.130 in 25 kg bags (yields 13.5 l plaster mortar, 1.35 m2 area at thickness = 1.0 cm), 48 bags/pallet

If stored correctly and dry, will keep for an indefinite period. If the material clumps together due to dehydration, this can lead to extra work during preparation; complaints on account of this are excluded. In winter, earth-moist goods must be stored so they are protected from freezing, otherwise workability during frost is impaired.

Mortar preparation
Add approx. 8–12% (earth-moist) or approx. 15% (dry) of water with standard rotary drums, turbomixers and pug mill mixers,
in small quantities also with the motor agitator or by hand. Information on the use of plaster machines can be found at

Plaster base
Clay plasters adhere only by mechanical force. The substrate must be stable, frost-free, dry, clean, free of salt, sufficiently rough and absorbent. If a primer is required, CLAYTEC RED (13.435-.430) is suitable. If necessary, the substrate may be moistened first (with a spray) to bind surface dust. Reed matting must be dry. Remove any previous coatings that form a film.

Plaster application method
Apply mortar using a trowel or spray on with a plastering machine. Thickness of application: basecoats 5–15 mm per layer, topcoats 6-10 mm. On concrete or overhead, strictly apply only 6 mm per layer. The consistency of the mortar must be matched to the application thickness. The use of YOSIMA clay designer plasters requires a well rubbed, flat surface (special preparation additionally required) or a thin overlay of fine clay topcoat 06.

Working time
Since no chemical setting process takes place, the material remains workable for several days if kept covered. It can be kept in plaster machines and hoses for the same length of time.

After application, it is essential to ensure that drying takes place rapidly, e.g. by means of cross-ventilation (all windows and doors kept open 24 hours a day) or drying equipment. Under critical conditions, drying must be documented in accordance with DIN 18550-2.
Details can be found there or in the CLAYTEC ‘Clay plasters worksheet’. We are happy to provide extra information.
Microbiological background concentration: Purely mineral product, earth-moist. For more details, visit,
‘Artikel Wohnung + Gesundheit’. We would like to point out that compliance with certain values cannot be guaranteed.

Subsequent processing
Subsequent plastering is carried out after the previous layer has dried, and not until any shrinkage cracks have been closed up. The surface may be coated with WHITE primer (CLAYTEC 13.415-.410) and CLAYFIX clay paint.

Work samples
The colours and textures of the various kinds of mineral clay plaster differ. Mineral 20 is not just earth-moistened Mineral 16, but an separate product with different granularity and composition.

The color and texture of the various clay plaster mineral delivery forms may vary slightly. 10.130 bagged goods may contain residues of straw.

The suitability of the substrate and application thickness must always be checked by means of a sufficiently large work sample.
Compensation claims, unless they result from factory mixing errors, are excluded.

For further information, see the ‘Clay plasters worksheet’.

DIN 18945-47
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