Construction work in winter - how to fight damp patches on the walls


The case of Hubert living in a Poznań area town shows that anybody performing plastering work in winter can encounter problems with wet plaster. According to construction experts, plastering work can be performed in winter provided that a temperature of at least 15°C is kept in the room and the humidity level does not exceed 70%. The building should be heated and have an appropriate ventilation system to extract moisture.

Hubert is having a small house with a surface area of approx. 120m² built for himself and his family. When the building was closed and windows and doors were installed, plastering work was started. It was performed at the end of October and the beginning of December 2010, when the weather outside was still quite warm for the time of the year. Problems started when a spell of wintry weather surprised everybody at the beginning of December. The temperatures remained below freezing for about a month and they were accompanied by enormous banks of snow. The thaw came in January and at that time, huge damp patches appeared on the walls of Hubert's house (see the photo).

In the construction sector, low temperatures outside usually mean that mortar takes a longer time to bond and harden. Hence, the problem with damp patches of newly laid mortar. At a temperature of approx. 8°C inside, it was impossible for the walls to become dry, and this is all the more so when considering the unfavourable weather conditions outside.

The owner of the house decided to use a condensation dehumidifier DH 751. At first, the device was placed in the dampest room with a surface area of approx 10 m². During the one-week long drying process, approx. 6-7 litres of water were collected in the room every day. Attention should be drawn to the fact that the higher the temperatures and the relative humidity level in the room are, the greater the efficiency of the condensation dehumidifier is. In this case, the temperatures in the room ranged from approx. 5-8°C, and these are the minimum temperature values at which the device can work. At the same time, the temperatures outside fluctuated from 0 to 8°C. Still, the damp patches became smaller after a week of using the dehumidifier.

Condensation dehumidifiers Master DH 751 may reach an efficiency level of up to 46 litres a day at a temperature of 30°C and the relative humidity of 80%. They are equipped with an electronic control panel and a built-in humidistat. The signal light indicating the filling level of the tank makes it possible to empty it at the right time. They are mostly used during finishing and renovation works.


To shorten the drying process, the owner also decided to use another dehumidifier – Master DH 25 – in another room. With such a high degree of dampness all over the building, It is necessary to use several dehumidifiers to achieve good results. The use of such devices is the only solution in such a situation before the arrival of warmer weather. Drying by means of heating and ventilation is a long-term process. Condensation drying is far more effective and economical. Additionally, in the case described here, an electric heater – Master B 3,3 was used to increase the efficiency of the dehumidifiers by raising the temperature in the room, thus accelerating the drying process. The use of mobile heaters is a perfect solution before the installation of the heating system in the building.

To find out more about condensation drying check dehumidifiers page.