Software vendor SAP wanted to expand its headquarters in Walldorf with a new building that offers a multifaceted office landscape for 550 employees on a gross floor area of 12,500 m² and could be realised within just two years. Using conventional construction it would have taken about twice as long for an office building of that size. So Stuttgart-based Scope Architekten concentrated from the outset on prefabrication and modular design. They began by exploring different construction methods - considering wood panel construction and steel-framed modules as well as a reinforced concrete frame with precast elements. Essential criteria were how much latitude each of the respective systems offer, how many options there are for individualisation in terms of module sizes, facade design and choice of materials, and how flexibly the respective suppliers could react to the architects' specifications. Furthermore, the modular system had to be feasible with the spatial concept for the offices, which includes large open areas.
Steel frame construction seemed to be the most suitable due to its versatile adaptability, large spans and fast production potential. Moreover, reference projects such as the Merck Innovation Center in Darmstadt - designed for the science and technology company by Henn Architekten and built of steel frame construction by the Swabian firm ADK Modulraum - show that individualised solutions can be realised even with prefabricated components.
To enable a comparison and at the client's request, Scope Architekten chose five bidders, with whom they entered into discussions about specific aspects of modular construction. At this point the architects also prepared the standard details and the preliminary design. The contractors submitted indicative price offers and elucidated their approach, the design and the time needed. Based on the indicative offers, team concept and procedure, the client decided to work with ADK Modulraum.
Plan concept and building volume
To meet the client's wishes, the architects developed a typologically diverse office concept that ranges from open office areas to group offices with micro offices for concentrated work to meeting rooms of various sizes. These spaces are distributed across two building wings with eccentrically positioned, light-filled atria, adjoined by office spaces organised in single and double bays. The communicative heart of the building is the "social hub" between the two office wings. It accommodates the circulation as well as conference rooms, plus it offers plenty of space for informal encounters.
The office wings and the central hub consist of hybrid steel-wood modules, with two different module lengths combined in the office wings and a host of individual module sizes in the hub area. A basic foundation of the concept was to coordinate the office grid and economically transportable module sizes. The architects set the office grid at 1.50 m, and based on this, the width of the module is 3 m, its height is 4.50 m and its length is 11 or 18 m -which resulted in weights of up to 35 t per module. Each office module extends across two bays and has one windowed and one windowless facade element.
The modular design is not only the basis of the building's structure but also plays a major role in its architectural expression. The block-like units' slight projections and recesses on each floor break up the building's form and rhythmically articulate the facades. Since each floor and each ceiling of the modules consists of a complete beam layer, no extra constructional effort was needed for the cantilevers. In the relevant modules, only the flange thicknesses of the steel beams were increased.
Using this simple principle of similar, stacked building blocks, recesses that can be used as balconies are created in the facade, and differentiated spatial relationships are created inside thanks to the staggered levels. Glass partitions at the atriums and between the office areas foster visual communication and uphold the open and transparent corporate culture.
Production and assembly
The architects developed a preliminary design that already took into account the construction method and involved the fabricator early on, and they also developed standard details. In October 2017, ADK took over the fabrication detailing and construction planning for the modules, as general contractor under the artistic supervision of the architects. Due to the many parameters - structural requirements; wall, door and window positions; MEP system requirements; different finish materials - each of the 224 modules is different. Each has its own set of plans and its own structural calculations.
The modules are made of hybrid construction: the structural parts under high static load are built of steel, while those less heavily loaded, such as the beams of the ceilings and floors, are made of wood. The modules were prefabricated in Neresheim, where the facades, ceilings and floors were planked with gypsum fibreboard and the windows were also pre-installed. Seven to eight modules (covered with tarpaulins for weather protection) were delivered by heavy transport to the building site every day. Due to the intense time pressure, the first modules were already set in place while the foundation slab was still being concreted elsewhere. The modules were positioned by crane and welded together with small steel plates. This took about 30 minutes per unit, enabling the building shell to be erected in just eight weeks. Since the modules were delivered with windows and temporary roof sealing as a weatherproof finish, the interior fit-out began immediately after placement. In this way it was possible to have many trades working simultaneously on the construction site. This proved to be a big advantage of the modular design, since the office building placed high demands on equipment, indoor air quality, cabling and electrotechnology. The modules' overall degree of prefabrication was roughly 60 %. With a longer lead time in the planning phase, the interior fit-out could have been more closely coordinated with the prefabrication to better exploit its potential.
The facades were installed on site. Powder-coated perforated metal sheets surround the entire building as a uniform outer enclosure. The individual "building blocks" are easily recognisable as modules shifted relative to each other, but the semi-transparent metal skin elegantly unites them. This underscores the industrial character of the building, but here too the industrial product was customised: the 1.4 × 3.5 m sheets were perforated in a special pattern whose proportion of holes increases continuously from 20 % at the bottom to 40 % at the top. The finely detailed sliding shutters are also made of perforated metal, allowing them to serve in lieu of classic blinds as sun protection. On the roof terrace, the construction principle is laid bare: here the steel frames are exposed and only support awnings (as shading elements) and perforated metal panels (as privacy screens). The architects also allude to serial and industrial aspects in their design and choice of materials for the interiors: with a wood floor made of veneered plywood strip flooring, with perforated metal sheets for ceiling linings and for the lobby stair guardrail made of black steel nets. The building was internationally distinguished with LEED Silver certification for sustainability.
Second building, same system
Two months later, Scope and ADK used the exact same system to create a second new office building for another 500 SAP employees in St. Leon-Rot, 10 km away. The architects adopted the module sizes and interior fit-out standards defined for the Walldorf site, but developed the form of the building from its environmental and built context. The offices are laid out in three bars that adjoin the western side of the elongated hub, thus defining a square in plan. Since the experience gained from the first building could be used directly, the already approved details were, for example, adopted for the second building without additional coordination. In this case, the new 12,600 m² four-storey building consists of 254 modules. The materials for facades and interior finish work are the same for both buildings, which in this case was also due to the time pressure. The overall planning efforts for the new building in St. Leon-Rot were significantly lower than in Walldorf. Nonetheless, the economic advantages of modular construction in terms of construction costs would only become apparent with a small batch of sorts, i. e. with a third or fourth project. The system is in principle capable of variation: the exact same system to create a second new office building for another and the building can be configured from small and large clusters; as the heart of the building, the hub can be individually designed and even the choice of materials is variable.
Serial individuality
Both buildings exemplify the potential inherent in modular construction, as a symbiosis of serial and customised production needing minimal time for planning and construction, for responding relatively quickly, as here, to strong corporate growth with high-quality architecture. Batch production and individual design are compatible when the architects are aided by a manufacturer who can implement their ideas with individualised solutions beyond the options in a standard catalogue, and when the client values architecture as an integral part of its corporate culture.
