The Line

Light-footed apartment building with super slender facade grid

The residential building The Line consists of 72 apartments and is located on the north bank of the IJ, in the newly developed area Overhoeks, opposite Amsterdam Central Station. Overhoeks is a dynamic living and working area in the vicinity of urban functions and the city centre. Buildings and urban greenery alternate in a campus-like layout, creating an attractive, varied living environment.

The Line is situated right in the centre of Overhoeks. The building has an omnidirectional orientation with a lively appearance all around. It is built on an underground parking basement. The main volume is slightly raised from ground level, which results in a light-footed appearance. Because of the high density of the district, an important starting point in the design was to maintain sufficient daylight at street level. Setbacks at the top of the building guarantee this quality, also for the lower floors.

The balconies are part of a continuous outdoor space around the building. Due to the expressively designed ceilings, these outdoor spaces seem to be part of the interior. A veil of thin sticks covers the building like an orthogonal cobweb. The identity of The Line is largely determined by its facade grid - composed of 60 mm thin balcony edges and 880 slender concrete columns. From the conceptual design phase, these components were conceived in ultra high performance concrete (UHPC). In an intensive collaboration with Hi-Con Netherlands the intended balcony slabs and facade columns have been further developed.

Extremely slender columns

For the columns, the limits of the possibilities of UHPC have been explored. The slightly tapered, square columns feel light and slender but at the same time stony and solid. They are 80 mm on three sides and only 60 mm wide at the front and up to 3.4 m long. In order to maintain the abstract image of a fragile grid, the fixings are kept as compact as possible. The columns are attached to the balcony slabs with steel dowels and brackets.

Spacious balconies

The balcony slabs are also made of UHPC. They are up to 6.5 m long with a cantilever of almost 2 m. Due to the dimensions of the facade grid, the balcony slabs and the columns have the same size of 60 mm in elevation. On the facade side, the balcony slabs have a nice curve at the bottom, making the outdoor areas feel even more spacious and natural. Circular openings created in the slabs on the top floors contribute to the light character of the building.

Cooperation

Orange Architects and Bouwbedrijf De Nijs approached Hi-Con at an early design stage. The engineering of the UHPC is done by Pieters Bouwtechniek. Due to the unique performance and properties of UHPC, cooperation in an early design phase is essential to obtain optimal results in terms of aesthetics, technical and financial feasibility.

Savings on material, weight and CO2

UHPC is a proven and durable building material with unique performance and properties with a lifespan of more than 100 years. The material has a lot of aesthetic potential, but is also extremely functional. UHPC offers possibilities for very slim and form-free construction and thus to save material, weight and CO2. In residential construction, less weight means more outdoor space and thus added value. This applies to new construction as well as renovation and transformation. Based on the most recent EPD (Environmental Product Declaration) of 2018, Hi-Con has calculated that a CO2 reduction of 25% per UHPC balcony is possible compared to balconies in traditional concrete.

Innovative solutions

UHPC is still rarely used in facades. The Line is a progressive and inspiring exception to this. The project demonstrates that the application of UHPC in facades becomes valuable and feasible with challenging, non-standard designs and dimensions. Designers and developers who want to push boundaries will find in UHPC a proven material for innovative solutions that add value.