Table of contents:
- All in good time
- Renovation measures on the facade
- Remedial measures for moisture damage
- Historical remedial measures
Video: Systematic Renovation Measures
A large part of the orders of the painter and plasterer take place in the building stock. Old buildings, historical or even listed buildings require a variety of renovation measures so that they retain their charm and comfortable living inside is made possible. Special renovation products make work easier.
Author: Susanne Sachsenmaier-Wahl | Photos: Baumit
Refurbishment measures on existing buildings place high demands on the craftsman. Because no old building is like the other, the measures must always be tailored to the individual property. Historic mortar mixes, construction methods and materials that have long been forgotten, or simply the ravages of time that have left (too) deep traces - the reasons that make facade renovation necessary are as varied as the resulting measures.
In order to make the work of the craftsman a little easier, Baumit, for example, has a comprehensive range of products for renovation, which has only recently been supplemented by some new developments. With the help of a guide, the company not only summarizes the most common damage and gives specific tips on how to repair it. The printing unit (which is also available digitally, see below) also contains advice on test methods and the scheduling of remedial measures.
All in good time
When working on existing buildings, it is often difficult not only the renovation measures themselves, but usually also their (time) planning and thus the calculation. In order to be able to make the right decisions regarding the scope of the renovation and the necessary procedure, comprehensive, meaningful masonry diagnostics is essential. As a rule, it is advisable to take a plaster sample from a representative location and analyze it. The function and future use of the building must also be inquired. Only then can the renovation measures and products be selected. At this point, accompanying technical measures, such as B. Appropriate dehumidification in poor ventilation situations should be considered.
Once the specification has been drawn up, the preparatory work can begin. Here too it is important to plan enough time. Drying times (for cleaning, e.g. 1 day / millimeter layer thickness) between the individual work steps must be strictly observed.
Renovation measures on the facade
Perhaps the paint is peeling or weathered, the top plaster may also have fine cracks, loosen or the plaster may be hollow. Then the renovation work on the facade should not pose any major problems. Then a coat of paint or a renovation is often sufficient.
If the existing cracks are larger than 0.1 millimeters, for fine structures up to 2 millimeters in maximum grain size or larger than 0.2 millimeters for coarser plasters, special treatment is required. In any case, cracks on the facade should be analyzed and assessed with regard to the damage pattern and the cause of the damage. Because how and with what cracks are repaired depends on the crack properties and the cause of the crack (structural cracks, dynamic cracks, static cracks).
In the worst case, the cracks found can be masonry cracks. Masonry cracks can e.g. B. caused by shrinking movements, subsidence or vibrations. Apart from wall surfaces, these cracks are particularly often found near weak points, such as lintel areas above windows or passageways. In the case of masonry cracks, it must be found out whether the cracks are static or dynamic (e.g. using plaster marks). If there are cracks in the load-bearing masonry, there are constant movements due to the no longer non-positive connection. So-called spiral anchors can be used to fix masonry cracks. Through this, the inventory can be largely preserved, which is particularly important in the area protected as a historical monument.
As an additional measure for setting spiral anchors, but also for the repair of cracks that only appear in the plaster, reinforcement plaster layers, which are applied in a layer thickness of approx. 5 mm, have proven their worth. The tension distributes the tensions from the substrate over a larger area, so that instead of a wide crack, a large number of very fine, physically unproblematic and invisible cracks are created. The effectiveness can be further improved by using fleece inserts, since the fleece reduces the movements in itself.
Often, however, the old plaster is still largely intact and the cracks that occur are not too wide. Then a technical crack repair can be useful. A distinction is made between filling and bridging systems. Purely mineral paints are always only filling, but can be made more elastic by adding organic binders. Organic coatings have a relatively high elasticity and therefore also have high crack-bridging properties. Unfortunately, the water vapor permeability used to be greatly reduced with these coats, so that detachment through moisture accumulation in connection with frost is possible. Newer systems based on silicone resin allow moisture to escape well from the substrate despite their bridging properties. Detachment through moisture accumulation in connection with frost,As is known from earlier crack-bridging paints, it is therefore unlikely. Nevertheless, before choosing such coatings - especially if the surface already has a higher moisture content - you should consult the manufacturer's specialist adviser to clarify the suitability for the respective renovation case.
And last but not least, there is another crack repair option that could be attractive to the client from an economic point of view: the application of a thermal insulation composite system. For example, if hollow layers in the area adjacent to the crack make it necessary to replace larger plaster areas, it may make sense to combine crack repair with thermal renovation. If more than ten percent of the old plastered space has to be removed on each side of the building, the requirements in accordance with the Energy Saving Ordinance apply anyway. By then at the latest, this renovation method will be almost without alternative.
Remedial measures for moisture damage
Damage to plaster and masonry can be caused, for example, by flooding, moisture, a lack of waterproofing, etc. If there is no influence from building-damaging salts, moisture regulating plasters are an ideal renovation option. Their high porosity and very good capillary water absorption capacity ensure a dry and functional plaster surface. These are suitable as top and bottom plaster and offer a high level of security for substrates subject to moisture to create a visually appealing surface. Even if there are building-damaging salts, they can be used if efflorescence on the surface of the plaster is not a visual problem. Thanks to their color, natural white moisture-regulating plasters offer the option of being used on damp surfaces as both a finishing and finishing coat. This makes them ideal for the paintless version. Because moisture regulating plasters should not be painted or coated in order to be able to fully develop their active principle.
Damaging salts and moisture damage the masonry and conventional plaster and literally push the latter away from the masonry surface. Restoration plasters WTA are able to be used on masonry that is extremely salty and damp. At first glance, a renovation plaster WTA does not show what the underlying masonry is struggling with. The plaster surface remains intact for many years. Because of the special properties of the renovation plaster, the damage-relevant evaporation zone is relocated to the underside of the plaster. Here the salts carried in the water have enough space to crystallize out within the pores. So they do no damage to the surface and the masonry can remove the moisture as water vapor to the outside. Plaster and paint remain dry and do not peel off.
There are a number of things to consider when it comes to processing and post-treatment so that renovation plasters can develop their special properties. So renovation plaster WTA should be applied about one meter beyond the visible damage zone. This “safety zone” helps to avoid damage due to the salt and moisture distributions inside the masonry that are not visible from the outside. Read here what needs to be considered when processing a renovation plaster WTA.
Historical remedial measures
In order to restore facades that have lost their original look and appearance due to an earlier refurbishment, plasters and mortars that have been tailored according to analyzes and the requirements of the preservation of historical monuments are offered. These are largely based on the building materials of past eras.
Even if the requirements of the Energy Saving Ordinance often do not have to be taken into account for historical objects, thermal renovation is still recommended to save energy. A purely mineral insulation plaster based on natural, highly hydraulic lime, for example, could be the solution here. The sprayable insulation layer follows the given masonry surface and therefore does not change the original character of the building.
You can find Baumit's renovation guide here: bit.ly/2WUK6KZ
Baumit has reorganized its renovation division under the name "Sanova". It comprises three areas: facade renovation, masonry renovation and historical renovation.