The Grassi Museum of Leipzig
Karl-Heinz Langer
Franz Dominic Grassi, after whose name the museum was called, comes from a family of tradesmen from Central Italy. During his youth and his professional training, he travelled often abroad and lived for a short while in London. In 1829 he became a citizen of Leipzig and created his firm for the sale of products coming from Russia, indigo and exotic fruits. After his father’s death, in 1847, the activity was widened embracing speculations and exchange operations. After his mother’s death, in 1854, he left the business activity and only dealt with the administration of his property.
The lifelong bachelor was buried in the ancient cemetery "Alter Johannisfriedhof" of Leipzig. He left to the town of Leipzig a heritage composed of around 2,3 million marks, thanks to which the town built many buildings, parks and monuments. An example of these is the "Neue Gewandhaus" (New textile emporium), the extension of "Städtisches (Kunst-)Museum" on Augustusplatz (Municipal art museum), the building of "Mende-Brunnen" (Mende Fountain) and last but not least the building of the "ancient" Grassi Museum, hosting nowadays the municipal library of Leipzig.
The "new" Grassi Museum located on Johannisplatz rightfully bears his name, considering that the collections of the ancient Grassi Museum, known well beyond the boundaries of the town, found their new site there.
The new Grassi Museum was built between 1925 and 1929 according to the project of Leipzig architects Carl William Zweck and Hans Voigt. Objects of applied arts, ethnology, regional geography and musical instruments are exhibited here, on a working surface extending over more than 27000 m². During the Second World War, the museum was heavily damaged by bombardments, but the collections were fortunately saved.
The restoration of the "new" Grassi Museum, for which an expense of 30 million Euros was estimated, made necessary another relocation. In January 2001 the exhibitions closed. During the refurbishment works, probably on until 2005, many surprises came up, as is often the case with the refurbishment of historical buildings, from the architectural and building viewpoint. In 2001 the restoration phase was started, after the temporary interventions made between 1990 and 2000. The task for the roofing and guttering works was assigned to the "Ornamentklempnerei & Metallbedachung" specialised firm of Redekin, Saxony-Anhalt.
KM Europa Metal AG of Osnabrück provided for the roof surface, more than 7800 m² of materials, mostly copper strips with a development width equal to 850 mm that during the installation with double vertical seaming, reduced to 780 mm after the folding. The roofing and guttering workers of Redekin chose, with the approval of the architects, a classical covering with panels with double transversal seaming, each 1500 mm long. The architects also maintained the original configuration of the ventilated roof under-structure, which, at the upper floor, is composed of a wood framework with a thickness ranging from 24 to 30 mm and a division layer. Considering that the panelling with double transversal seaming concerning heat dilatation has the same pattern as a strip covering, according to the technical standards for the guttering and roofing sector of ZVSHK (Central Association for Hygienic Sanitary, Heating and Air Treatment systems), panels were installed with fixed hooks only in the upper part and in the other cases with sliding hooks.
For the protection of monuments heritage the decision was taken to keep the measure of the axis resulting from the original covering. 780 mm, as a matter of fact, would not meet the technical standards imposed for the guttering and roofing sector and concerning the buildings with a height lower than 20 m, for which a maximum width of tiles equal to 620 mm is allowed, with a 0,6 mm thickness. However considering that 0,7 mm greater thickness and the double transversal seaming guarantee a greater rigidity against wind strength, anyway noise or vibrations due to wind or undulations are excluded.
Undulation is in fact a subject always at issue. Copper reflection in fact at the start highlights the smallest planarity defects, which become less evident as the surface becomes dull due to oxidation. Since this work is hand made, and it is not a prefab surface industrially manufactured, the formation of waves and bumps cannot be totally avoided.
Since in the area of dormers the roof was irregular, it was not easy to make the bill of quantities. For example, 2600 m of oblique cuts were necessary for conical series of small importance. Impressive numbers nevertheless also concerning the total length of ridge ventilation, equal to around 960 m. It was necessary to insert, by welding, around 70 conical ventilation tubes with a diameter at the bottom up to a maximum of 670 mm; in the internal courtyard it was necessary to cover more than 100 window sills, install more than 700 m of coatings for gutters and manufacture around 50 conical covers for gutter vents.
Just for the gutter more than 1100 gutter-carrier were made in alloy steel. Out of a total of around 800 m of rainspout, 140 m around were also covered. In addition, 43 historic piezo-metric tubes with a hole for cleaning are part of the supply and of the assembly, up to 2,40 m long. Since these tubes do not have to be borne by the main tubes, they are partially supported by 12 mm threaded pins.
At present, the material used considerably affects costs mainly when the construction projects are great, as in this case. Also, the costs are influenced by the high quality of the product used, by the guarantees supplied, by the competent and gratuitous counsel provided on the construction site, as well as by the flexible and punctual delivery.
Collaboration with great partners
To carry out such an important project punctually and knowledgeably the "Ornamentklempnerei & Metallbedachung" specialised roofing and guttering firm chose two efficient and reliable partners.
KM Europa Metal AG of Osnabrück supplied the Tecu-Classic brand copper strips, mainly in the special 850 mm x 0,7 mm size. The producer guarantees quality control according to plant’s internal standards and to Lloyd’s Register Quality Assurance system in compliance with DIN ISO 9001. All Tecu products are furthermore certified according to their ecological compatibility by the "Arbeitsgemeinschaft Umweltverträglichkeit Bauprodukt e.V" (Association for construction product’s ecological compatibility) and guaranteed by "Zentralverband Sanitär Heizung Klima" (ZVSHK) (Central Association for Hygienic Sanitary, Heating and Air Treatment systems). In addition to the collaborators of the Technical Consulting Centre of Osnabrück, an assistance service was always available on the construction site in case of unexpected events.
Schrag Bauklempnerei- und Bedachungsartikel GmbH of Leipzig (with a branch in Dresden as well) is a specialised firm with a long tradition in the field of roof materials. Thanks to more than 3000 items, and 30 years of experience in the field of folding and high technical skills, great capability in the supply of materials and reliability in deliveries, as well as a balanced price/performance ratio, the firm of Dresden worthily became a partner in this project.
This kind of report can only make a list of obtained results and analyse the problems linked to construction. One thing is for sure: for the roofing and guttering workers who made the works (and also for all the other participants to the project) the Grassi Museum unquestionably represents a crucial reference letter.
This view from the top shows the total dimension of roof surface to cover, 7800 m². The drawing is oriented to the North, the top side corresponds to the Northern side of the building.
Photographed from a skyscraper in front: the Eastern view of the Grassi Museum is massive.
On the foreground, one of the two cupolas of the internal courtyard in the Western part of the building, surrounded by a roof with regular angulations. The bottom part of this roof surface shows an inclination by 20°, the top part by 38°.
But "the devil has had a hand in this". Roof geometry, also in the area of cupolas of the internal courtyard, is partially very complicated. The picture shows the staggered vertical seams and the insertion of the chimney, the development of a valley and roof vents welded and riveted.
The development of internal courtyard cupola’s base illustrated in the previous picture. Thickness of details made necessary, before the construction, to create samples in order to combine all aspects, both technical and aesthetic, fitting them into the style of the work.
Originarily the roof of Grassi Museum had 83 triangular dormers. The architects of Leipzig instead considered creating just 30 of them. The picture shows part of them. On the roof surface inclined by 38° another dormer, with rectangular plan and six windows, coated with copper still polished.
Even if the quantity of triangular dormers was clearly reduced, architects strictly met the requirements imposed by the Institute for the protection of monuments.
The connections of cornices with the coating in natural stones of the tower of the stairwell were pre-sealed with lead: a classical alternative to modern sealing agents in order to comply with tradition.
The development of this dormer required a considerable craftsmanship skill in order to reproduce it perfectly.
