Remediation Solutions

What needs to be taken into account when carrying out repairs in line with the preservation order and what do these objects look like.

The facades of existing buildings come to life when we look at our history. Here the skills of the builders and craftsmen of the time in which the building was built are reflected and they testify about the type and possibilities of the building materials available at that time.

As a result of weather and environmental influences, the original composition of the old plaster inventory has changed over the course of decades. Salts damaging to the building, moisture and mechanical effects, aging and also changes in the building fabric - as a result of changes in use - have an impact on the condition of the building fabric and the condition of the plastering mortar.

It is therefore necessary to provide materials for the restoration, renovation and reconstruction of historical monuments as well as the restoration of particularly worth preserving historical objects that meet the requirements and objectives of the preservation of historical monuments. On the basis of these requirements, special products with adapted grain and binder compositions are to be designed.

Individual solutions are required

The implementation of individual solutions poses a challenge for everyone involved. Before facades are repaired, the various aspects of later use, any existing monument preservation requirements and the condition of the building structure must be clarified.

Appropriate studies of the existing plaster form the basis for the new concept of the future plaster system.

The mortar properties that can be determined today are no longer identical to the properties of the mortar from the time it was manufactured. The historical mortar additives of the old master craftsmen are difficult to detect today. In the case of well-preserved old mortars, the use of such additives can be assumed.

Even with today's advanced methods, the determination of the original properties of historical plasters and their composition is only possible to a limited extent and makes economic sense. The binders and additives used were generally obtained, manufactured and used on site. When hardening, the binder can react alone or in conjunction with the local aggregate. These reactions in particular are no longer comprehensible in detail, or only to a limited extent. Basically, however, the mortar analysis, the age of the mortar samples and the condition of the old mortar - taking into account its location on the property - allow conclusions to be drawn about its original composition.

Object example # 2: BV Munich, Bergmannstrasse

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Who writes stays

In addition to taking sample material, the documentation of the appearance of the surface represents a crucial basis on the way to recreating a corresponding material. The current appearance provides information about both the handicraft technology used and the change in structure and surface over time due to weathering. You can tell from the different appearances of the same structure on a building that every craftsman has his own individual handwriting, that sometimes the sand had a slightly different sieving line, that the mixture was sometimes a little bit rich or poor in binders. The most important goal of the facade surface to be redesigned is to reproduce this existing appearance.

Furthermore, the technical parameters of the rendered plastering mortar must be adapted to the repair work. This means that different properties may be required, which depend on which measures are required for the repair or reconstruction. If a renovation plastering system WTA is used as a plaster in the outside area, the plastering mortar must be water-repellent. If you only work on the inventory, then the properties have to be largely adapted to the inventory. This is the only way to avoid future damage.

Craftsmanship in demand

The appearance of a structure depends very much on the handicraft technology. This means that the replacement mortar should be processed using traditional handicraft techniques. These may also have to be learned again.

Everyone involved must be aware that both the replication of plastering mortar and the use of traditional handicraft techniques are both time-consuming and economically complex. In order not to exceed the specified budget, suitable compromises have to be found.

In this way, the appropriate solution for the relevant property can be found in a dialogue with everyone involved. At the same time, it becomes apparent that there are limits to what can be implemented for all sides. Not all requirements can be met and taken into account equally. It must be contractually agreed if one will deviate from the normative requirements or the general rules of technology in order to meet the requirements for the re-adjustment. All risks and consequences must be known to the client and accepted. Any necessary deviations from the findings also require a corresponding regulation.

Permanent development

Industry is also looking for justifiable solutions to stay within the economic budget. It is checked whether there are alternative solutions through the selection of suitable binders, modern additives and factory production, which nevertheless ensure that most of the requirements are met and also enable machine operation. The craftsman is often ready to add special additives - such as animal hair or very coarse grains - on the construction site, the admixture of which is not possible via production plants. The material recipes used for this can be specially tailored to these additions.

If one takes into account the aspects shown here, then it can be repaired in accordance with the monument. However, this can only be mastered together with architects, planners, the contractor and the monument authorities. Many examples show how the renovation can succeed.

Author: Constance Brade

Object example # 3: BV Medical Vocational School Dresden

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