Full-scale construction prototype of the NEST HiLo shell roof

This full-scale experiment investigates the feasibility of spraying a textile reinforced thin concrete shell using a lightweight flexible formwork composed of a tensioned cable net as falsework and tailored fabric as shuttering. This one-to-one (with a bounding box of 20m x 10m x 5m) prototype can be seen as the dress rehearsal for the construction of the roof of the NEST HiLo project.

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The development and realisation of this full-scale, one-to-one prototype of the first layer of NEST HiLo's thin concrete shell represent a key milestone for the project, demonstrating the viability of the proposed lightweight, flexible formwork to form a complex concrete surface structure.

The purpose of this experiment is to investigate

  • the engineered material system, bespoke sprayed concrete and tailored carbon-fibre reinforcement mats, to achieve the extreme geometry of the shell;
  • the logistics, including sequencing of construction, involved in scaling up the concept of a tensioned flexible formwork;
  • the effectiveness of the control algorithms, supported by point-cloud scanning, developed to map the flexible formwork to the designed target geometry; 
  • the quality of the resulting architectural concrete on the thin and large surface structure.

Professional partners have been brought together to mimic real-life conditions so that the feasibility of this extreme construction innovation can be assessed.



ETH Block Research Group [BRG]
ETH Chair of Mathematical and Physical Geodesy
ETH Automatic Control Laboratory


Marti [general contractor]
Bürgin Creations [concrete works]
Doka [scaffolding]


Jakob [cables]
Bruno Lehmann [rods + cable net components]
Blumer Lehmann [timber]
Dafotech [steel supports + plates]
Bieri [fabric cutting + sewing]


ETH Zurich
NCCR Digital Fabrication
Holcim Schweiz




Cable-net and fabric formworks for concrete shells

Cable-net and fabric formworks for concrete shells

This project investigates the feasibility of using both large cable nets with a secondary system of fabric shuttering as well as fabric directly as a formwork for concrete shells. These lightweight formwork systems reduce the need for seperate foundations of the formwork and allow unobstructed space underneath the shell during construction.

Active control of a cable-net formwork

Active control of a cable-net formwork

The use of tensioned formworks in concrete shell construction can reduce the demand on foundations, promote usable and unobstructed internal space during construction, encourage formwork re-use for repeated application, and greatly eliminate the material waste often experienced with traditional timber formwork and falsework. To understand the behaviour of such a net system prior to the pouring of the wet concrete, this research project investigates the fabrication, control and measurement systems needed to define a geometrically accurate net prior to concrete pouring, such that it will displace under the wet concrete self-weight to the correct final shape. The internal pre-stress forces as well as the forces and deflections at the boundary points also need careful consideration.


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