Mapei guidelines for the installation of cement-based smoothing compounds during cold weather & winter

January 12, 2024

Mapei has produced a set of guidelines on the application of cement-based screeds during the winter and periods of cold weather. The drying process of cement-based smoothing compounds can be severely affected by ambient temperature and humidity, particularly during winter months. It is, therefore, important that the installer is fully aware of potential issues and how to adjust the normal process to ensure a successful installation.

Mapei guidelines for cold weather & winter

The reaction of the cement constituent part of a smoothing compound when combined with the required liquid (latex or water) part is known as hydration. When the liquid element is mixed with the cement constituent part, the smoothing compound is formed. Apart from hydration, there are a number of other reactions that occur at the same time including exothermic (heat generation). As the reactions evolve, the combined process of the hydration process binds the individual particles of the mixture to form a solid mass, with the exothermic reaction causing the product to dry. For these reactions to occur, including and importantly the exothermic reaction, the minimum temperature of the environment in which it is installed must be a minimum of +5°C and remain at this temperature or above whilst the product is drying.

Drying times can be affected by a number of factors, including the type of substrate to which it is applied, and importantly humidity, temperature and ventilation.

During winter months these types of products should not be applied after midday in areas where there is limited or no heating and when overnight ambient temperatures will drop to below 5oC. If the products are subjected to temperatures lower than 5oC the exothermic drying process will stop, thus preventing the curing of the binders, which can affect the final strength of the smoothing compound and may also result in the occurrence of long term issues.  

If the partially dry product is subjected to temperatures below 0oC any remaining water within the smoothing compound can freeze resulting in the formation of ice crystals, which will damage the material.

If required, and to ensure the site conditions conform with the required British Standard, a dry source of heat can be utilised to assist during the drying process, however this must be left on until the product is completely dry. Please also note that not only is heat required, but good airflow is also essential to ensure that the saturated humid air is constantly removed thus allowing the continuation of the drying process.

There are also a number of other procedures that can be utilised to help avoid cold weather issues:

  1. All materials must be stored in dry conditions and be fully protected from frost and water. 

    1. The temperature in the area can be raised using a portable dry source of heat. 

    2. If water mix products are being used ensure that tepid water is used and not cold water direct from a tap or an onsite water bowser. 

    3. Use fast drying smoothing compounds to reduce drying times. 

    4. Increase airflow/ventilation utilising fans if required to help remove saturated air to aid with the evaporation. Do not use heaters to increase 
airflow as this will force dry the surface resulting in cracking occurring. 

    If the daytime temperatures are above the required level, but may drop at night, do not apply any smoothing compounds after midday to ensure that the products have initially set prior to the night-time cold weather. 

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