Renovation interior plaster | "Neues Schloss" Waldthurn
Successful restoration of a listed building
The plastering of this property was a massive challenge in terms of planning, coordination and execution. This can only succeed if, as here, architects and craftsmen with many years of experience work closely together. The result is a beautiful, exemplary refurbished building that fully demonstrates the value and purpose of heritage conservation.
Historic and damp masonry
The listed "Neues Schloss" Waldthurn (Upper Palatinate), a former princely castle from the 17th century, could finally be renovated thanks to its inclusion in an EU funding programme. However, the poor condition of the building made it necessary - before the internal plastering could be carried out - to work on the roof and the massively damaged masonry: tonnes of crack injection mortar were used.
The specification of the monument preservation authorities for the interior renovation was to use lime-based plasters and to preserve the old plaster as far as possible. On the ground floor in particular, the masonry was very damp due to the lack of waterproofing. The analysis of masonry samples by the maxit laboratory revealed that only small quantities of damaging salts were present, so the site management decided that lime plaster with the addition of trass should be used instead of restoration plaster. The addition of trass improves the moisture resistance of lime mortars and reduces their tendency to effloresce.
Insulation with a system
Firstly, the friable masonry mortar had to be scraped out over a large area by around 2 - 3 cm. It was replaced with maxit mur 956 trass lime masonry mortar, which also has a positive effect on the statics of the masonry. In the case of large excavations, wall sections were inserted using the masonry mortar.
The preservation authorities wanted to avoid the use of modern products in this building, so the plaster bases, for example, which were necessary on non-load-bearing substrates, were made of reed!
As plaster thicknesses of 4 - 6 cm were required to level the fissured masonry and the service life of lime plasters is 1 - 2 days per mm of plaster thickness, the construction schedule was quite challenging. Once the maxit ip 393 trass-cement priming mortar had dried, the first base coat of plaster was applied. The decision was made in favour of the lime-trass undercoat plaster maxit ip 392 (4 mm grain), as the shrinkage is lower with coarse-grained plasters than with fine-grained ones. The actual undercoat plaster layer was then applied - with maxit ip 390 lime-trass plaster in a thickness of approx. 20 mm. This was applied again in a thin layer and felted. In rooms with high visual requirements and when connecting to existing plaster, maxit ip 315 purcalc lime thin-layer plaster was applied thinly and felted.
In the dry masonry of the upper floor, it was possible to work mainly with maxit 381 pluscalc. Time was saved here, as it can be applied in a single layer, even in varying thicknesses.