rcc heritage buildings

On many historical buildings, non-plastered bricks or masonry is a distinctive element of the façade design. In this case, a health balance needs to be found between renewal and restoration. Cleaning work generally needs to be planned and verified on sample surfaces. It is only after this stage that it is possible to identify those stones that need to be replaced and the extent of the necessary restoration.
The repairs of cracked, friable or even weathered joints is usually necessary on these kinds of façades. Here, modern mortars can be adapted to the historical brickwork and also mortars can be developed based on traditional and historical procedures. After careful deliberation of the advantages and disadvantages, waterproofing products can be examined with respect to their suitability and, where appropriate, they can even be adapted to the required water-repellent level so that there is adequate re-drying potential. Excellent examples for our expertise in this field are the Deutschordensschloss Malbork (Marienburg) in Poland or the wharf warehouse B (the current Maritime Museum Hamburg), both of which are UNESCO world heritage sites.

Regardless of whether or not the base is rendered or has visible brickwork, it is one of the structural components of a building that is subject to the most loads.

The most important negative influencing factors are rising damp and splashwater containing salt water. Damaged or missing water proofing notably can cause substantial damage, starting with moisture horizons, salt efflorescence through to massive crumbling of the rendering. Often, damage is not limited to the outside area. The moisture that has penetrated the base can reach the inside walls by means of capillaries or diffusion and be discharged into the room. Over time the moisture absorption and discharge of the wall becomes balanced, but this does not mean that no damage will occur. The even water vapour through the wall puts pressure on the building materials and leads to a continuous increase in the salt deposits and an increase in the room air humidity. The consequence could be unpleasant odours or damage to historical inner wall surfaces or furnishings.

The Remmers specialist planning department is able to examine these moisture flows in detail and simulate them if necessary so that suitable measures to protect the substance of the building can be recommended.

Historical mortars are sometimes no longer able to satisfy today’s utilisation and safety requirements; however it is difficult to assess their durability because there is usually little knowledge about old mortars and their formulations.

At the same time, renders and mortars form the visible character of our buildings and are valuable testaments to historical building materials and construction technologies. Therefore, the goal of restoring and/or repairing many historical structures is not only to conserve the original substance but also to create substitute or reconstruction mortar and renders that replicate most of the properties of historical mortars, regain a former condition, duplicate its form and function and reuse the original materials and methods.

This is where the Remmers specialist planning department can help: Depending on the building, the existing old mortar is analysed and replicated to approximate its form and function as closely as possible. The analysis method is provided by the accredited Bernhard Remmers Institute for Analytics, the interpretation of the analysis results in close coordination with the experts of the mortar departments at Remmers GmbH that also reconstruct the original findings. The decision is made by the building owner and monument preservation office after samples have been taken on the building.

Since ancient times, buildings and sculptures have sported paint coats and coloured edging. They served (and still serve) as design elements on the one hand and as a protective and wear-resistant layer on the other. The importance of the protective function, notably against disintegration damages - has increased in recent times in light of emission-related weathering damage.

The binding agents available today for colour paints on principle allow the opportunity to find compromises between the key points of the monument preservation ideas and the technical optimum. Often lime-based coats are suitable to realise the former. Over the past 20 years, it has been possible to develop purely mechanical modified lies, lime paint systems that demonstrate much better disintegration resistance compared to ‘normal’ lime systems. The technical optimum can be achieved most easily using high-quality silicon resin paint systems that now allow enormous creative freedom. Somewhere in-between are silicates and mineral paints whose use in the concept phase needs to be deliberated carefully with respect to advantages and disadvantages.

Also, or in particular, historical buildings often are not or deficiently water proof on the base that has contact with the ground. This means that high levels of moisture can be absorbed by the affected building materials and transported. Levels of moisture that go above and beyond the ‘normal’ compensation moisture, are not generally healthy for any building materials. In these cases, a reduction of the moisture level is always a sensible restoration goal because this not only improves the durability of the repair work, it also considerably slows down the weathering of the substance of the historical building. It is difficult to use modern, bitumen-based sealing products on historical objects. This kind of material is almost not reversible and its properties are not suitable for historical structures.

However, the mineralalogical sealing systems that have been further developed in recent years are! Where applicable, it is even possible to create this reversibility by means of a few planing ‘tricks’.

Remmers is the absolute specialist for the production of stone conservation agents and everything else connected. These products are used on valuable cultural goods across the world. This is not possible without planning, although the usual structural examination are seldom applied here. These are usually special examinations that need to be carefully planned, executed and interpreted. The Remmers specialist planning department has extensive expertise in this field based on long-standing tradition.

In addition to mature conservation technologies with respect to desalination, strengthening and swelling of natural stone, the growth in know-how about natural weathering and decay in past decades has led to the development of further monument conservation standards. Whilst earlier monument preservation goals in the majority of cases focussed on restoring the original condition within the meaning of an aesthetically pleasing reconstruction, today, they primarily focus on the protection and conservation of the original substance and its historical importance. Understandably, this approach has a considerable impact on the building materials and processing technologies used. In many cases, the material volume has been reduced, however the quality standards have risen. In many cases intervention into the original substances is much less invasive than earlier. One example is the almost complete lack of the transfer of stone substitution mortars. This almost automatically leads to the need to stabilise the original substance onto which the material should be transferred. Consequently, the various preservation and repair measures are mutually dependent. This requires individual damage mechanisms and types to be addressed more specifically that in the past. The Remmers specialist planning department is the right partner.

Information about the load bearing capacity of an historical masonry work is very important for securing and modifying old building substance. Load-bearing parts of historical buildings, like walls and columns, frequently comprise two-shell natural stone or brick masonry work. Whilst the outer scale is bricked ‘normally,’ in the majority of cases there is a ‘filling’ or stone chips and a high percentage of mortar on the inside of these parts. Above and beyond the strength and deformation properties of stone and mortar, the load-bearing behaviour is also influenced by many other parameters.

Selecting the right mortar for repairing these parts or to asses the suitability of the strengthening agent to enhance the load-bearing capacity of vaults requires a high level of expertise that the Remmers specialist planning department has proven time and again in a series of objects including St.Peter in Cologne and the Church of the Holy Sepulcer in Aachen.

There are numerous methods available today for cleaning historical surfaces, for instance dry and wet procedures, the use of chemicals, high and low-pressure methods, special methods e.g. gommage, and vortex systems and laser equipment.

However, none of these systems is used systematically to clean larger surfaces inside historical buildings. Either, a lot of water needs to be used or a lot of dust is created. However, some inner areas were cleaned with procedures that lead to an unacceptable increase is costs due to the prior removal of all furniture, careful covering of sensitive areas with plastic film or even the installation of almost air-tight tents.

Cleaning with a laser is a common method for cleaning decorative building elements, however the price-performance ratio is still unsuitable for large, even surfaces. Also, in some cases, colours were changed to an unacceptable level due to the combined action of the high-energy jet with colour elements and the glauconite in some building materials. All these problems can be avoided with natural rubber-based Peel-Offs. The Remmers specialist planning department uses these to plan interior cleaning of historically valuable surfaces without impeding further utilisation of the rooms during the cleaning work.

One special example for the well planned and executed use of modern conservation methods comprises the hand-finished roof tiles dating from the end of the 12th century that were used on the 1200 year old Carolingian Einhard Basilica in Steinbach in the Hessian region of Odenwald.

The contacted company and the leading restorer collaborated excellently and, in an initial step, catalogued and mapped all the tiles so that their condition could be classified. The tiles that are collected in pallet cages were stored in a 100 m³ dipping tank on site to rinse out any earlier unsuitable conservation agents by means of washing. After cleaning, the dipping tank was covered to allow the roof tiles to dry out for a period of approximately six months. This is followed by a strengthening process with silicic acid ester KSE 300, likewise in the dipping tank. Based on parameters earlier obtained in tests, time frames for the work processes were planned and safety precautions were taken.

After the saturation and reaction process, the basilica with the strengthened roof tiles were covered again.

Some of the wooden roses, dragons and mascarons were heavily weathered and destroyed which made it necessary to reconstruct their forms and structures. It was important to find a method to conserve the original material of this decorative element as far as possible. The roof beams were impregnated preventively against wood-destroying insects. Further protective measures were developed for impregnating the wooden construction. The wood cladding and the floor were refreshed and protected with the colourless hard wax oil. Finally, the façade was renovated.

Summary: The Wang temple in multiple ways is such an unusual structure that it is worth taking the time and effort to maintain its original state as far as possible for future generations.

This is just one example of the challenges of restoring historical wood constructions. Here, too, like for all other types of building materials that are worth preserving, it is important to combine necessary expertise about destructive environmental influences and know-how about preservation and protection methods.

Cracks in the brick wall are more frequent the older the building. The causes of the cracks are manifold. Temperature stress, foundation settling and vibrations are just some of them. Regardless of the cause of the damage in each case, a crack in brickwork always has a substantial impact on the static system and should be repaired to prevent further damage.

Up until a few years ago, cracks in brickwork were always repaired by replacing the cracked stones and restoring the load bearing masonry system with new mortar. This means that one or two stones to the left and right of the crack need to be removed and then replaced once the old grouting mortar has been removed. Often, these repairs were evident and in many cases the original load bearing capacity could not be adequately restored.

Since the introduction of the so-called spiral anchor system, parts of the masonry work can be connected to each other simply and highly efficiently, so that the brickwork is strong again. The spiral anchors only represent a small intervention into the damaged masonry, because they can be installed into the joints. Even cracked stones can be recycled. This is also one of the reasons why spiral anchors are widely accepted in the field of monument preservation. Cracks in façades and near lintels, openings or curved sections can be repaired successfully with minimal invasion.

If decorative parts, figures, balusters, stucco elements etc. are to be or must be replaced, for instance to protect the originals from the weather or to replace repeatedly inserted and partly destroyed elements, the preserved originals can be shaped.

Casting compounds that are able to replicate the details of the originals down to the finest surface structures are necessary for the actual reconstruction. Also, it is necessary to fabricate special, pourable and shrinkage-compensated mortars that can also do this and that are also suitable for replicating the appearance of the respective building material.

The procedure for drawn stucco elements is completely different. If the shape of the original and been copied and a template made, mortar is required, notably for external stucco, that can best approximate the processing properties of the gypsum mortar used in the past but which has a much higher weathering resistance.