Facades in building construction - assessment and repair planning of reinforced concrete, masonry and rendered facades
Due to its exposure, the facade of a building, along with the roof cladding and the outer basement walls, is one of the parts of the building that is subjected to the greatest stress. At the same time, the facade is often an indicator of maintenance, as it visibly represents the state of preservation of a building.
While historical buildings often feature elaborately designed facades made of natural stone and brick masonry or (lime-cement) plaster, reinforced concrete and steel/glass constructions increasingly prevailed as construction materials in facade design in the second half of the 20th century.
Facade cladding with prefabricated reinforced concrete elements was widespread in both residential and industrial construction in the 1970s and 1980s due to the diverse design possibilities and the robust, low-maintenance construction. After around 35 to 50 years, many of the buildings constructed at that time are now reaching the age where fundamental repair work is required.
Common problems of these facade claddings are often more or less pronounced corner and edge spalling due to steel corrosion with insufficient concrete cover. Fortunately, problems occur less frequently in the support area of the facade panels.
Flat facade claddings were often used as lost formwork in the construction of cast-in-place concrete walls, the connection of the facade panels was then made by anchor reinforcement, which was directly integrated into the cast-in-place concrete load-bearing shell. In contrast, cassette profiles and reinforced concrete transoms (e.g. parapet panels or sun protection elements) were often secured to the facade with anchor bolts or shear dowels. As a rule, the use of stainless steels was planned for the anchoring elements, which should permanently prevent damage in the area of the support structure. On site, however, simple structural steels were sometimes used, as a result of which the support structure of the reinforced concrete parts can be damaged by steel corrosion, especially in the area of anchor bolts and shear pins. The problem today is that the support structure can usually only be inspected with great effort and that a (partial / selective) dismantling of the facade slabs was not taken into account as planned.
In addition to the purely technical repair of the facade cladding, building physics aspects (especially thermal insulation) and often fire protection requirements must also be taken into account in most cases.
LPI Ingenieurgesellschaft mbH has been intensively involved in the condition assessment and repair planning of facade claddings for several years. In addition to historical facades, such as the Academic Art Museum at the University of Bonn, the focus is primarily on reinforced concrete facades with exposed aggregate concrete facade panels, such as the high-rise building of the Cologne Regional and Local Court.