Brand: RA&Sons

RASTAW is a cement free premixed powder based on hydraulic lime, sand and micro fibres. Whether used as a repair mortar or plaster for conservation work, or as a general purpose mortar or plaster for new work, RASTAW’s breathable nature makes it ideal for exterior or interior applications.

Surface Preparation

All surfaces should be clean, dry and dust free. Any surface contaminants like grease, oil and efflorescence must be removed in order to promote adhesion. RASTAW can be used as a repair filler for any holes or cracks or to level any uneven surfaces.



RASTAW should be mixed with a mechanical paddle mixer to achieve a smooth and lump free consistency. Mix in a clean bucket using approximately 5.5 – 6.0 litres of clean water per 25Kg bag. When used as a mortar gently wet the substrate to aid adhesion. When used as a plaster wet the substrate and apply to a thickness of 5-10mm, further coats must be applied on the same day before the previous coat has dried. When using as a dehumidifying plaster RASTAW can be built up to a thickness of 20mm but an anti-salt treatment must be applied first.



Do not use RASTAW:

  • As a structural mortar, it is for repointing only.
  • Never add cement, gypsum or other binders.
  • Do not use when the air temperature is below +5°C or above +30°C


Natural Hydraulic Lime Based Transpirant Mortar For Restoration

Packaging & Storage

RASTAW is supplied in 25Kg bags and can be stored up to 12 months in a cool dry place, in its original unopened packagingrest

Safety Notice

Before using RASTAW it is recommended to consult the product safety data sheet available on request

Technical Data

1280 kg/m³
<1.0 [mm]
Light Brown
Coverage (Theoretical)
13 [kg/m²] each 1cm thickness
Mixture Water Content
Pot Life
2 Hours approx at 20°C - 70% RH
Compression Strength After 28 Days Curing
Conforms to CS II as per UNI EN 1015-11
Adhesion to Surface
>0.3 [N/mm²] average - according to UNI 1015 - 12
Permeability to Water Vapour
12 - According to UNI 1015 - 19
Class WO - According to UNI EN 1015 - 18
Fire Resistance
Class A1 - as per EN 13501 - 01
Thermal Conductivity
0.59 [W/mK] - UNI EN 1745
None - According to norm 88/379
The data and statements in this information sheet refer to laboratory tests in our possession, conducted in standard environmental conditions. Practical applications on site according to these conditions of use may result in different data readings. Due to the wide variety of possible uses and applications, the end-users should independently determine the suitability of the material for their specific purpose prior to use. R.A. & SONS Manufacturing Ltd. reserves the right to make technical modifications of any kind without prior notice.

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