Knauf

Task

The Spreebogen (bend of the River Spree) concept

The Chancellery bears testimony to a significant gesture, a unique symbol - nevertheless: decision-makers divided the original concept of the architect team, Axel Schultes & Charlotte Frank, of creating a "Band des Bundes", a ribbon of federal buildings, as a "courageous self-expression of the democratic state", into three individual pieces: Federal Chancellery, Forum and Alsenblock. In 1993, the architects submitted a magnificent idea for the International Ideas Competition. Their town planning design, which intends a kind of "clasp" over two kilometres in length and around 100 metres wide, as an "urbanistic, effective image of the regaining of state unity in Germany", was considered a splendid symbol of East and West unification. Two separate competitions were launched for the Federal Chancellery and the Alsenblock, the home of Paul-Löbe and Marie-Elisabeth-Lüders: the winners: Axel Schultes & Charlotte Frank and Stephan Braunfels. However, the heart of the district, the public forum with space for cafés, restaurants and shops, was not included. No executable planning for this exists to this day.

Multilayered floor plan

As monolithic as the building seems from the outside, the interior presents a complex spatial structure, characterised by openness and intimacy, by astonishing perspectives and a well-calculated management of the light. The sensual waves of the ceiling become a pictorial metaphor of the original town planning idea of the "Band des Bundes", a circular sweeping staircase turns out to be a complex spatial composition, clearly structured offices provide the necessary variability for concentrated as well as team-orientated work.
The core building initially receives the visitor with a spacious entrance hall. Here, you can glance unhindered up to the skylights, which clearly distinguish the wings. The centre of this quadratic construction is determined by a cube that is laid out in a circular pattern and which is divided into different segments and encircled by wide staircase entrances. A series of differently modelled, free-standing columns, which sweep from the ceremonial courtyard and the Chancellery Garden and through the facade to the interior, were also utilised as space-defining elements. They guide the visitor to the main “square” in the core of the building. A snaking, waved ceiling serves as a linking element throughout the various levels – from the entrance hall at the ceremonial courtyard to the foyer which resides at a higher level in the Chancellery Garden. It is from here that you can access the two-storey conference hall. The third and fourth upper floors accommodate meeting rooms and archives. The actual Chancellery starts above this and is accessed by the so-called "sky lobby". The administrative wings are located in the north and south sides. A total of 13 conservatories subdivide the comb-like wings. Generally speaking, six similar-sized offices form one unit, which is located on a short corridor.

Spatial works of art with optimum surfaces

The interior design of the Chancellery signifies a complex structure comprising strong geometry juxtaposed with organic form. The effect is founded on perfectly structured passages as well as precisely designed surfaces. The demands placed on the architects and the site management with regard to the plastered surfaces and details were equally challenging. The surfaces of ceilings and walls, predominantly produced using cast-in-situ concrete, were thus coated accordingly with Knauf plaster. The hand plaster, Rotband, was also used alongside the machine-applied plaster, MP 75, (around 40.000 m²), which was mainly used in the stairwells, and Universal-Finish (around 40.000 m²). The plastering work was executed by the Rebentisch GmbH, Berlin. The wave-shaped ceiling, partially divided into cassettes, generates a strong impression in the entrance area. This massive volume flows throughout the entire depth of the building. The contracting company chose to use Knauf Universal-Finish here.

The sophisticated machine logistics and particularly light, single-layer, dust-free processibility of Universal-Finish, coupled with the smooth and strong surface quality of this thin plaster, boasts unbeatable advantages compared with conventional dispersion-filler-based techniques, which usually have to be applied in several layers and then sanded down.

Three silos with silo jet systems, one PFT G4 and two PFT G5 plastering machines, formed the backbone of the logistics technology. With an average material thickness of 3 – 5 mm, the optimised thin plaster properties provided the reliability required for creating the towering walls or the curved ceiling surface in the entrance hall. To guarantee the best possible plaster adhesion, the concrete surfaces, which were partially soiled with concrete release agents, were pretreated using the bonding agent, Knauf Betokontakt.

Diverse lighting situations emphasize the optical effect of the sweeping, white ceiling. Straight edges on the ceiling edges and on the cassette-like recesses, or precisely structured transitions to the integrated lighting, are evidence of a careful, skilful execution.

With a round staircase, Axel Schultes & Charlotte Frank have created an extremely effective spatial composition in the fifth, sixth and seventh floors of the building: the "sky lobby" is set out like a small amphitheatre. Sweeping balustrades, staggered or single overhangs and open footbridges form astonishing perspectives. Smooth, white walls and ceilings enhance the effect of this refined spatial geometry and allude to the considerable plasticity of Knauf Universal-Finish. Whereas the curved, projecting balustrade cornices are provided with their intended, precise structure by manual plastering with Knauf Rotband.

A snaking, waved ceiling serves as a linking element throughout the various levels - from the entrance hall at the ceremonial courtyard to the foyer which resides on a higher level in the Chancellery Garden. It is from here that you can access the two-storey conference hall. The third and fourth upper floors accommodate meeting rooms and archives. The actual Chancellery starts above this and is accessed by the so-called "sky lobby".

The administrative wings are located in the north and south brace. A total of 13 conservatories divide up the comb-like wings. Generally speaking, six similar-sized offices form one unit, which is located on a short corridor.

Solution

Dry construction wave ceilings

The thorough implementation of the consistent architectural concept, right down to the last detail, was also standard for the dry construction work. The intended overall effect of the ceiling in the fifth, sixth and seventh upper floors of the building can be seen as a fixed component of the original town planning space idea of a "bond of the federation”: like a calm wave, the ceiling surface flows "unhindered" through all the rooms of a floor. Alongside interesting lighting and good acoustics, with this ceiling design the architects have created spaces of an intimate nature. The design and construction of the ceiling represented a challenge for the system developer, Knauf, and the contracting company, Lindner. It proved to be an advantage that the selected Knauf system could be used as a "conceptional framework" upon which to develop concrete special solutions.

The base framework of the convex and concave-shaped ceiling surface was produced from a pre-fabricated coarse grid of CD profiles 60/27 – superimposed with a fine grid that is then clad with two layers 9.5 mm thick Knauf boards. The details, which were carefully developed and coordinated especially for this project, in conjunction with Lindner and Knauf, also included that the ceiling should be a convincing component of the architectonic special idea. The partition walls between the offices and the corridor are glazed in the upper area so that the grand gesture of the ceiling design remains alive.

The substructure was therefore levelled throughout by Lindner, then fitted and finally cut to meet the area of the glazing. After the glazing had been fitted, the ceiling cladding was applied. In doing so, specially pre-fabricated metal plates, developed and produced by Lindner, guarantee a precise formation of the ceiling edges in the area of the panes of glass.

Freely projecting wave peaks in the corridor coupled with the external facade complement the elegance of the suspended ceiling. The principle, design and shape were developed and produced at Knauf.

The special structure consists of a UA sliding grid 50/40/2,0. Pre-fabricated steel constructions made of light metal are combined with the convex-shaped CD profiles of the general grid of the ceiling. In doing so, the UA profile takes the load, while the CD profile enables the uniform line of the ceiling surface up to the "detached" wave peaks. This creates an overall cantilever arm structure, to which a pre-fabricated Knauf plaster shell is subsequently fixed. Around 600 square metres wave ceiling was produced in this manner.

Combination of cavity space and raised floor The communication technology in the Chancellery complies with state-of-the-art technology and offers the required flexibility of the modern office building. The basic prerequisite for this is a technically practical combination of cavity space and raised floor systems, so as to guide the installation cables to any point in the room without a problem. The advantage of this combination: while cavity space flooring systems have a consistent layer of screed, raised floor systems enable quick access to all installations at any position. Two systems by Lindner using Knauf components were implemented: the cavity space floor HoBo 35 FE GS 600 (around 3600 m2), as well as the raised floor DoBo 600 A1 (around 11000 square metres). The choice of flooring system was also critical for the conceptional design approach of the architects in the area of the office wing. A concentrated working atmosphere, which could be adapted according to the working processes, was to be created. Generous double doors enable opposing offices to be "connected", so that work situations can arise across the corridor, similar to a group office.
The system DoBo 600 A1 is used in the corridor area of the two office braces. Steel support feet, height-adjustable and set in a grid 600 mm apart, carry the freely positioned raised floor boards. These are constructed as "steel tubs" which include a filling compound by Knauf. Underlying base plates promise good acoustic insulation. The compatibility with the cavity space system HoBo 35-FE GS-600 proved to be an impressive advantage in the Federal Chancellery. The steel supports of this system are also set in a grid at distances of 600 mm.

This makes it possible to lay individual boards of the raised flooring within the cavity space flooring system in order to use these as access hatches. If several raised floor boards are laid in a row, a channel can be efficiently created inside the cavity space flooring. Reinforced gypsum boards, designed especially for the application area of cavity space flooring, then form the accessible base for the 35 mm thick Knauf flowing screed. Adapted electrics also offer utmost flexibility. The system HoBo 35-FE GS-600 complies with the following fire protection properties: F 30 from below and F 90 from above. The high-quality longitudinal sound insulation enables the positioning of good sound-insulating walls, always guaranteeing a peaceful working environment in the Federal Chancellery.