Making single-layer coating or lime mortar in cold or damp weather

SolutionMaking single-layer coating or lime mortar in cold or damp weather

System description

The application of single coat mortars or lime mortars in certain environmental conditions, such as rain, low temperatures, or high relative humidity, is subject to an increased risk of whitish staining.

These stains are called efflorescence, are the result of a mechanism called carbonation and usually occur in the first few days immediately after application of the material.

Carbonation occurs when the salts released during the setting of the cement dissolve in the mixing water, migrate to the surface of the single-layer lime mortar and react with atmospheric carbon dioxide, giving rise to calcium carbonate, which is white in colour.

The speed at which the mortar dries has a major influence on the appearance of stains.If it is sufficiently fast, the setting salts remain in the capillaries and do not come out. On the other hand, if it is slow (due to the aforementioned environmental conditions), they reach the surface of the mortar and form whitish deposits or efflorescence.

Dry wind has an important influence on the appearance of the spots.

Although carbonation does not alter the mechanical performance of the single-layer mortar, it creates an aesthetic problem, which is all the more noticeable the darker the colour of the coating.

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The solution consists of covering the façade to be clad, i.e. placing tarpaulins and protecting it from wind and rain so that the curing process is carried out in such a way that the external conditions do not affect it so much.


Wait until the material has completely set and hardened (28 days after application) and then remove the stains by washing with acidified water (hydrochloric acid in a ratio of 1:4 with water).

Once the solution has been applied, rinse with plenty of water.

In case the carbonation has been severe and the stains are difficult to remove, applyREVAT® FILM/ REVAT® FILM SLX, to restore the aesthetic characteristics of the single layer mortar or lime mortar respecting its texture and properties.


  • Do not apply in the following conditions: when there is a risk of rain or frost, at temperatures below 5°C, with high ambient humidity.
  • Protect coatings against the risk of rain and/or frost, at least until the tenth day after application.
  • Try to apply light colours in cold weather, when efflorescence is less visible.