Membrane structures, also known as lightweight structures, are spatial constructions made from tensioned membranes. They are used for roofs, façades, free-standing buildings, building envelopes, skylights, indoor ceilings, and accent enclosures. Their distinctive visual appeal allows designers, architects, and engineers to create elegant and highly aesthetic forms.

Optimised for structural efficiency, these spans require minimal primary support, making them cost-effective and environmentally sustainable. Suitable for infrastructure, culture, sports, entertainment, commerce, offices, residential, and private use, they offer limitless possibilities in application, design, and functionality.

Compared to traditional buildings, tensile structures provide column-free, light-filled spaces, rapid assembly, reduced costs, and exceptional durability. Robust and weather-resistant, membranes perform reliably in diverse climates, with some lasting over 30 years.

Environmentally Friendly – Most materials are recyclable.

High Reflectivity – Reduces heat absorption.

Low Sunlight Absorption – Minimises overheating.

High Light Transmittance – Can be translucent or transparent.

Natural Daylight Utilisation – Reduces reliance on artificial lighting.

Enhanced Thermal Insulation – Multi-layer constructions improve efficiency.

Lightweight – Requires minimal structural support.

Self-Cleaning – Maintains appearance with minimal maintenance.

UV Stable – Resistant to degradation from sunlight.

Customisable Appearance – Available in various colours and printable surfaces.

Long-Term Stability – Durable and weather-resistant.

Tensioned structures curve between supporting elements, reflecting the flow of tension forces within the membrane. These curvatures are anticlastic, as membrane materials can only bear tensile forces, not pressure. The anticlastic curvature, combined with mechanically applied pre-tension, stiffens the surface, providing statically calculable stiffness. The greater the deformation, the lower the pre-load forces required to handle external loads like wind and snow. This load-bearing principle, illustrated by Friedemann Kugel in the brochure "Arbeitskreis Textile Architektur", is described as follows:

• A single brick causes a kink in the rope at the suspension point.

• Multiple bricks create a polygon, merging into a continuous curvature (chain line) under direct load.

• Upward loads turn the rope into an upward-facing system.

• Combining both rope systems creates a simple cable net that can carry both upward and downward loads.

• Multiplying this simple cable net with parallel cable shafts in both directions forms the anticlastic curved rope net, which mirrors the form and load-bearing behaviour of membrane structures.

Types of Membrane Structures

The variety of membrane forms is vast, but membrane structures can generally be divided into two main types: mechanically pre-tensioned and pneumatically pre-tensioned.

• Mechanically pre-stressed structures create saddle-shaped (anticlastic) surfaces, such as pre-tensioned sails.

• Pneumatically pre-stressed structures create air-inflated cushions, tubes, or air halls with synclastic surfaces.

Some membranes are supported by single cables or cable nets.

Membrane structures are secondary structures, stabilised by a primary structure made from rigid materials like steel or wood. This primary structure ensures stability, even when the membrane structure is removed.

Form-finding

Formfinding is the process of creating the desired shape from flexible membrane material. Achieving the optimal aesthetic and operational form is essential for the project's development. It is typically an iterative process combining shape modelling and civil engineering principles. Historically, formfinding has been done through trial and error, soap film models, hanging chains, scale models, stocking materials, and now, formfinding software.

Design Development

To create an ideal, aesthetically pleasing, and cost-effective membrane structure, it is crucial to collaborate closely with all involved parties—client, architect, and membrane construction company—early in the process. The architect’s initial sketches set the framework for functional requirements and desired aesthetics. From this, the specialist engineer of the membrane construction company develops a preliminary design, which includes the necessary geometries and construction elements, such as supports, bracing, and anchorages. A budget can then be determined based on this draft. The final design, aesthetics, functional requirements, and budget are reviewed in collaboration with the client and architect.

Structural Analysis

Unlike conventional structures, the final shape of membrane structures is determined by statics. Therefore, design planning must be closely coordinated with static analysis to achieve an optimal economic and creative result. Due to the long lifespan of the materials, membrane structures are classified as permanent structures and must meet the building regulations of individual countries, including load assumptions for wind, snow, and climatic conditions.

The static calculation takes into account the data from form determination, considering various load cases and the material's biaxial expansion behaviour. This results in a verifiable static calculation. Membrane structures are subject to deformation under external loads (e.g. wind and snow), which must be absorbed by connection points to the load-bearing structure, conventional structures, or foundations. Unlike traditional buildings, the material's weight (around 1–1.5 kg/m²) is negligible, making membranes highly susceptible to wind loads. This is compensated for by the membrane's shaping and pre-stressing, which places special demands on the supporting structure and foundations. The bearing capacity of the subsoil is typically less important than in traditional construction, with tensile loads dissipated by heavy-duty foundations or special ground anchors.

Engineering

The static calculation defines the material’s required tensile strength, often using a combination of steel and ropes for the supporting structure. The design can be freely chosen, as long as geometric and construction connection points are respected. The optical lightness of the roofing allows supports and girder systems to be dissolved into fine grid structures or replaced by ropes. Other materials like aluminium, stainless steel, glued wood, or steel constructions can also be used.

Once the static calculation is approved by the authorities, construction drawings are prepared, requiring coordination with the planner and client. In addition to accurate geometry, sufficient attachment points for mounting and clamping tools are essential. The structure and membrane are typically pre-prepared for installation, similar to a prefabricated house.

Fabrication

Based on the geometry required by the static conditions and architectural intentions, the layout model is developed using special FEM programs. Before this, the tensile strength of the material is tested, and biaxial expansion behaviour is determined through tests. This is essential for obtaining authority approvals and ensuring the structure can be tensioned as calculated.

Templates are cut using automatic cutters, and welding processes for materials like ETFE, Glass/PTFE, and PVC/Polyester require modern machinery and skilled staff. Quality control procedures are crucial to ensure seams can safely withstand calculated loads. Final inspections, including optical and measurement checks, are conducted, and materials are packed according to specific requirements to avoid damage during installation.

Installation

A plan must be developed early in the engineering process for installing the membrane, identifying fixing points and the membrane’s size. Installing pneumatically or mechanically tensioned structures requires expert knowledge. Additional static calculations may be needed for the installation steps, considering the bearing structure.

During installation, the material should be handled carefully to prevent damage. Membrane elements are fixed to the design points and tensioned step by step. The final tension of the structure is then verified. Weather conditions, such as strong winds or low temperatures, can affect installation, and work should stop if conditions are unsafe for both the structure and workers.

Maintenance and Inspection

Membrane structures require relatively little maintenance compared to conventional buildings including maintenance, inspection, cleaning, testing, and repairs for membrane structures: