Restoration of Rathausen’s monastery
Rathausen - Switzerland
Dating from 1254, the masonry of the listed monastery of Rathausen near Lucerne had suffered severe structural deterioration. Both inside and outside, significant damage to plaster and masonry had to be repaired in order to ensure the continued, needs-based use of the building complex by SSBL, the Swiss charity for the severely disabled headquartered in Lucerne. In order to protect the masonry from salts and moisture, an injection of paraffin was planned in the initial invitation to tender, together with application of a restoration render. However, the high labour input and cost meant that eventually this option had to be rejected. Together with the Canton of Lucerne and the heritage preservation authorities, the principals sought an alternative solution, finally opting for the moisture-control render system Exzellent STP from MC.
The effect of Exzellent STP
Between 2015 and 2017, each of the walls of the Rathausen monastery was repaired inside and out by the construction company Knöchel + Pungitore AG, with Exzellent STP render being applied from ground level to the lower window line. First of all, the base area around the building had to be freed from the old plaster. The subsequent render covering was applied using Exzellent STP 540 as the pre-spray primer, Exzellent STP 500 as a machine-applied top coat and Exzellent STP 750 for the required fine finish. The advantage of the salt transport effected with Exzellent STP is decisive, especially for building base areas carrying a high salt load.
The salts are constantly attracted from the masonry to the surface of the render without encountering any meaningful resistance. Thus the base is permanently protected from salt-related damage. The façade above was repaired where most needed, with the entire surface then being painted with a highly diffusion-promoting paint.
In the interior, an “STP strip” was installed together with a new floor on a damp-proof course. The humidity is now regulated over the area around the floor-wall connection by that Exzellent STP skirting. The cloister was also completely rehabilitated inside and out.
Easy-to-use yet innovative salt transport render
Exzellent STP has been designed in such a way that moisture, including dissolved salts, is released from the masonry into the ambient air before any damage can occur – made possible by a unique network of interconnected macro and capillary pores. The salts crystallise on the plaster surface without damaging its structure and can easily be brushed or washed off. The Exzellent STP render system enables the fast and effective repair of damp and salt-laden masonry and can be applied directly to the damp wall. It is resistant to all water-soluble salts found in buildings. The use of Exzellent STP also means that costly waterproofing measures such as provision of a secondary damp-proof course can be avoided. With the total success of the renovation work, the monastery building near Lucerne has returned to its former splendour and is very much back in service.