There is also a need for living space in Frankfurt am Main. For this reason, not only the roof was raised during the conversion of an old paint factory into ten residential units. The basement rooms were also extensively renovated in order to convert them into living space. However, the architects encountered a problem in the Rödelheim district that many building owners fear and that often makes renovations very difficult. The basement walls, which were to be insulated for the new residents, were damp. Jan Lüthje, area manager at Xella, reports: "Here, however, not only was groundwater pressing upwards, but the water was also coming from the street." Because a tram runs on it, no structural intervention to protect the old factory was possible here. All in all: a tricky situation. "It quickly became clear: this house can only be renovated from the inside and the first thing we need is a complete assessment of the subsoil."

In addition, basement walls are often not only damp, but also contaminated with nitrates, chlorides, sulphates or other salts. These substances usually originate from a salt-contaminated subsoil and creep into the masonry together with the rising damp. The result is a white, fluffy and crystal-like coating on the inner surface of the walls. A sight that builders do not want to see. Then it becomes even more difficult to renovate and insulate the walls permanently and healthily for the occupants. Either the walls have to be elaborately drained or additional material has to be placed between the wall and the insulation. ExSal Therm glues and reinforces with one product. The material is easy to work with and eliminates the need to dry out the masonry.

Less salts, higher fire protection

The solution in Frankfurt was therefore ExSal Therm boards from Multipor. They are open to diffusion and capillary-active, because they consist of 90 percent pores. This means that the pores absorb the moisture and salts from the masonry. The moisture then evaporates on the panel surface and the salts are deposited in the pores in the long term.
At the same time, the desalination panels have excellent thermal insulation properties. They raise the surface temperature of the wall and thus increase living comfort. In times of climate change and the resulting requirements, this is a considerable additional benefit that is automatically included. 
Because the mineral insulation boards are also made of non-combustible material, they increase the fire protection of the building. In addition, the recyclable material is free of pollutants and evaporating substances. Allergy sufferers will be pleased to know that the Multipor boards are capillary-active and thus eliminate the risk of mould growth.

This is how the basement renovation was done

First, the loose old plaster had to be removed from all the walls to be insulated and the joints of the underlying masonry had to be cleared of small parts with a steel broom. EXSal Therm lightweight mortar was then applied in several layers. This created the basis for the ExSal Therm mineral insulation board. The renovated walls were then reinforced with lime plaster and painted with interior silicate paint. Electrical cables are most easily installed over the skirting boards. Alternatively, they can be laid on the levelled wall and the desalination panels slotted in accordingly on the back. The heating system was also installed in the wall. For the later occupants, the following applies: Furniture must be placed at a minimum distance of two centimetres from the wall. This is always recommended for optimal air circulation. In addition, there is also extra ventilation in the converted cellar rooms for the exchange of room air. However, this is not a basic requirement.

Renovating after floods and heavy rain

"For us, this conversion was not only a special challenge from a technical point of view, but also because the contractors used the newly developed Multipor ExSal Therm boards here for the first time," says Lüthje, a trained master painter. "The processing company was thrilled at how easy the material was to work with." And that it was available at all: other insulation material manufacturers surveyed had cancelled for the complex business. The Multipor material has unique selling points that other manufacturers cannot offer.

The experience gained by the Xella colleagues now flows into many other projects. Wherever there is a river nearby, houses are latently threatened by possible flooding. This is also true in locations with rising groundwater. The threat of heavy rainfall can occur anywhere and at any time. It does not even need a body of water nearby.