Introduction: The Connection Is the Facade
When people look at a building, they notice the panels: the colour, the curves, the way light moves across the surface. As facade designers, we notice what they cannot see. Behind every well-resolved facade sits a quiet system of anchors, brackets, rails and frames that carries the weight of the panels, resists wind, absorbs movement and keeps water out. If that system is wrong, even the most beautiful panel becomes a liability.
This guide explains how fibre-reinforced polymer (FRP) and glass fibre reinforced concrete (GRC, also written GFRC) panels are attached to a building’s structure. It draws on the design and manufacturing approach of ShapeShift Technologies, which designs, engineers and manufactures fibre-reinforced facade panels and has delivered more than 350 projects across 18 countries. Whether you are an architect, engineer, builder or developer, our aim is to help you understand the options and ask better questions early, when changes are still cheap.
The Facade and the Building Envelope
The facade is the visible outer face of a building: its proportions, materials, openings and finish working together. The building envelope is the wider system. It is the complete boundary between inside and outside, and it must manage water, air, heat, sound, fire and structural movement.
The attachment system is where these two ideas meet. It is the physical link between the architectural skin and the primary structure. On a typical lightweight panel facade, the build-up from outside to inside looks like this:
- The facade panel (FRP or GRC)
- The fixings that hold the panel
- The substructure, made up of rails, brackets and secondary framing
- A drained and ventilated cavity
- The weather barrier and insulation
- The backing wall and primary structure
This arrangement is known as a rainscreen. The outer panel sheds most of the water, the cavity lets the rest drain and dry, and the inner barrier is the second line of defence. Most FRP and GRC facades follow this principle, so the attachment system has to work with the cavity, not against it.
Rainscreen, Building Skin and Double Skin: Clearing Up the Terms
These terms are often used interchangeably, but they describe different things, so it pays to be precise.
Rainscreen is a specific wall design principle. The outer panels shed most of the rain, but they are not expected to be watertight. Behind them sits a ventilated and drained cavity, and behind that is the true weatherproof barrier and insulation. Any water that slips past the panel joints drains away, and the wall dries out, so moisture never has a chance to settle. FRP and GRC panels fixed to rails or a subframe are classic rainscreen cladding.
Skin facade is not a precise technical term. It is usually used in one of two ways. Loosely, it means the building skin, which is the outer layer of the building envelope. In that sense, a rainscreen is one type of skin, alongside sealed render, masonry or a glass curtain wall. Occasionally it is shorthand for a double skin facade, which is a different system entirely: two complete layers, often glass, separated by a larger air space that is used to manage heat, ventilation, sound and daylight rather than just rain.
| Term | What it means | Main purpose |
|---|---|---|
| Facade | The visible outer face of the building | Appearance and identity |
| Building skin or envelope | The whole outer boundary, including the facade layers | Weather, thermal and acoustic control |
| Rainscreen | Outer panels, a drained and ventilated cavity, and an inner weather barrier | Moisture control |
| Double skin facade | Two full layers with a wide air space between them | Thermal and environmental performance |
Sections through each wall, with the outside at the top. The rainscreen drains water through its cavity, while the double skin uses a wide air space to manage heat, ventilation, and sound.
In this guide, “rainscreen” is the correct term for how FRP and GRC panels are attached and drained, because the attachment system must hold the panels clear of the wall and keep the cavity open. We use “building skin” or “building envelope” when we mean the wider outer layer, so the two are never confused with a double skin facade.
Why FRP and GRC Suit Modern Facades
Before looking at fixings, it helps to understand the two materials, because their properties drive every attachment decision.
FRP is a composite of glass fibre in a cured thermoset resin. Architectural FRP panels are typically a thin single skin of around 3 to 8 millimetres, or a deeper monocoque shell of 10 to 50 millimetres, and they weigh roughly 5 to 32 kilograms per square metre. They can span very large areas, with panels up to about 2.4 by 10 metres, and they are the natural choice for deep cantilevers and double-curved geometry that other materials cannot deliver without awkward joints.
GRC combines Portland cement, fine sand and alkali-resistant glass fibre. Panel skins are usually 12 to 20 millimetres thick, supported by integral ribs or a light steel stud frame, and panels are commonly made up to about 3 by 6 metres. GRC reads as concrete in colour and texture, and it is tested as non-combustible, which matters for many external walls.
The key comparison is weight. Conventional precast concrete panels commonly weigh 250 to 500 kilograms per square metre. Because FRP and GRC are so much lighter, the supporting steel, the fixings and the crane lifts can all be smaller. In our experience, those savings on the structure and installation often outweigh any difference in the panel rate itself.
The Forces an Attachment System Must Resist
A good attachment design starts with a clear list of what the connection has to cope with.
Dead load. The self-weight of the panel must be carried down to the structure through a defined load path. Lightweight panels reduce this load, but it still needs a reliable, rigid support point.
Wind load. Wind creates pressure and suction on the facade, and on thin panels it is usually the governing action. Fixings must resist both directions, and corners and edges of a building often see the highest suction.
Thermal and moisture movement. Materials expand and contract. GRC moves roughly 10 to 20 microstrain per degree and FRP roughly 15 to 30, and cement-based materials also swell and shrink slightly with humidity. If a panel is held too rigidly, the stress has nowhere to go and cracking or distortion follows. Flexible connections and correctly sized movement joints are the answer.
Building tolerances. Real structures are never perfectly straight. Structural deviations of around 20 millimetres either way are common, and the attachment system must absorb them through adjustment so that the panel face still lands true.
Long-term behaviour. FRP under sustained load needs checking for creep and deflection limits, and all fixings must resist corrosion over a design life that is typically 50 years for facades.
The four actions above are the starting list for every fixing design: weight, wind, movement and building tolerance.
The Main Attachment Systems
There is no single correct way to attach a fibre-reinforced panel. The following six approaches cover most projects we see. How they are grouped can vary between suppliers, so treat this as a practical classification rather than a rigid standard.
The four methods below are drawn as wall sections with the outside at the top. Each holds the panel clear of the structure on rails or brackets, and the choice depends on the look, the installation speed and the panel type.
1. Stud Frame System (GRC)
The stud frame is the standard solution for large GRC facade panels. A thin GRC skin is connected to a light steel frame, and the frame is then fixed to the building structure. The skin is not bolted directly to the frame. Instead, it is connected through flexible anchors, so the frame can move independently of the skin.
This is the most important idea in GRC detailing: the skin and the frame behave differently, and the connection must allow for that. The system lets us make large, thin, light panels while keeping stresses away from the skin.
2. Gravity and Flex Anchors
Inside a stud frame system, two kinds of anchors do different jobs. The gravity anchor is rigid and carries the weight of the panel. The flex anchors, usually L-shaped steel rods bonded to the skin with a pad of GRC, hold the skin in position against wind but allow it to move relative to the frame.
The design principle is simple: carry the weight at a small number of fixed points and let everything else float. Getting the number and position of these anchors right is a job for engineering analysis, not guesswork, which is why finite element analysis is part of how ShapeShift Technologies proves panel sizes, fixings and wind loads rather than assuming them.
A close-up of the stud frame connection: the gravity anchor stays rigid, while the flex anchors bend so the skin can move against the frame.
3. Hook-On Rail Systems
In a hook-on rail system, horizontal rails are fixed to the substructure and the panels hang from them using brackets. The advantages are speed and adjustability: panels can be lifted into place and hooked on, then fine-tuned for alignment. For projects with many repeated panels or a tight program, this method can shorten installation time considerably.
It also suits open-joint rainscreen designs, where the gaps between panels are deliberately left unsealed to ventilate and drain the cavity.
4. Concealed Undercut Anchors
When the architect wants a clean, uninterrupted face with no visible fixings, concealed undercut anchors are a strong option. A hole is drilled into the back of the panel, shaped so that the anchor expands into a cone-shaped recess and locks in place. The panel is then supported from behind on rails or brackets.
This approach requires a panel with enough thickness and strength at the fixing point, so it is chosen early in the design, not added late.
5. Visible Face Fixings
Exposed mechanical fixings, such as screws, rivets or bolts through the face, are the simplest and most economical method. They are quick to install and easy to inspect. The trade-off is appearance. Designers who choose this route often turn the fixings into a deliberate part of the facade rhythm, with consistent spacing, finished heads and colour-matched caps.
6. Monocoque FRP Panels on a Secondary Subframe
Large FRP panels, particularly monocoque shells, are stiff enough to span big areas without a separate frame of their own. They are typically connected to a secondary steel or aluminium subframe, which then ties back to the primary structure through brackets. Slotted holes and adjustable brackets handle tolerance, and the connections are designed to allow for the greater thermal movement of polymer composites.
Because FRP is so light, the connections are often fewer and smaller than on a heavier system, which reduces thermal bridging through the insulation layer.
Choosing the Right System
The best system depends on the combination of material, geometry, fire requirements and structure. As a starting point:
| Situation | Typical approach |
|---|---|
| Large GRC panels with a concrete look | Stud frame with gravity and flex anchors |
| Repeated panels, fast programs, open joints | Hook-on rail system |
| Clean face with no visible fixings | Concealed undercut anchors |
| Large, curved or cantilevered shapes | Monocoque FRP on a secondary subframe |
| Budget-driven or easily inspected facades | Visible face fixings |
These are guides, not rules. Real projects usually mix more than one approach, for example using a hook-on rail across the main wall and a bespoke subframe at a curved corner.
A simple decision path for finding the likely system. It mirrors the table above and is a starting point, not a substitute for engineering.
The Substructure, Cavity and Drainage
The fixings are only part of the story. The substructure behind the panels, made up of rails, brackets and anchors back to the primary structure, has to be coordinated with the cavity, which is typically 25 to 50 millimetres deep. That cavity lets water drain and air move, and it must not be blocked by bracket positions or insulation.
Brackets that pass through insulation create thermal bridges, so fewer and smaller connections are better, and this is one of the quiet benefits of lightweight panels. Flashings at openings and edges direct water out of the cavity, and the weather barrier behind must stay intact where fixings penetrate it. We always review these junctions with the full wall build-up in view, not the panel in isolation.
Fire Safety and the Attachment System
Fire performance is assessed on the complete wall system, not just the panel. That includes the backing wall, supports, insulation, cavity treatment, fixings, sealants and coatings. A good panel can be undermined by a poor cavity detail.
The material difference matters here. GRC from ShapeShift Technologies has been tested to AS/NZS 1530.1 and achieved a result of not deemed combustible, which is the test the National Construction Code points to for external walls of Type A and Type B construction. FRP is a polymer composite and is not non-combustible; it has achieved Group 1 under AS 5637 and B-s2, d0 under EN 13501-1, which are strong results but a different category. Where a non-combustible external wall is required, GRC is the substrate to specify.
Cavity barriers, junction details and fixing materials should be coordinated with the project fire engineer early, rather than being left to shop drawing stage.
How a cavity barrier at the floor line interrupts the rising path of hot gases inside a ventilated wall. Exact barrier positions and ratings come from the project fire engineer.
Installation: Where Design Meets the Site
A connection that looks good on paper must also be buildable by a crew on a scaffold or a swing stage. A few practical points shape our detailing:
- Setting out. The structure is surveyed first, and grid lines are established so that every panel is fixed to the same reference.
- Tolerance adjustment. Slotted holes, shims and adjustable brackets absorb the difference between the drawn structure and the built one.
- Lifting. Lighter panels often avoid the need for heavy crane time, and panels delivered on load-rated stillages arrive protected and ready to lift.
- Sealing and finishing. Where joints are sealed, the sealant must be compatible with the panel surface and allow for movement.
A site or factory mock-up is one of the most valuable steps in the process. It lets the team test the fixings, the tolerances and the appearance before committing to full production.
A Design and Specification Checklist
Before detailing begins, we recommend settling the following questions with the project team:
- Is the element external or internal, and what is the fire requirement?
- What are the panel sizes, shapes and curvature?
- What are the wind zone, building height and structural system?
- What tolerances can the structure realistically achieve?
- Should the fixings be concealed, visible or a mix of both?
- What is the cavity depth, and how will it drain and ventilate?
- What finish and colour are required, and how will they be maintained?
- Will a mock-up be built, and by when?
Common Mistakes to Avoid
Restraining movement. Fixing a thin panel rigidly at too many points invites cracking. Allow for movement deliberately.
Ignoring tolerances. Designing as if the structure were perfect leads to site clashes and forced fits.
Assessing the panel instead of the system. Fire, water and thermal performance belong to the whole wall.
Deciding fixings too late. Concealed fixings, panel thickness and cavity depth are linked, and each is hard to change after tooling begins.
Leaving the manufacturer out of early design. Buildability is cheapest to fix while the geometry is still being decided.
Conclusion
An FRP or GRC facade succeeds or fails at the connection. The panel gives the building its character, but the attachment system gives it safety, durability and a long service life. By understanding the materials, the forces involved and the available systems, from stud frames and flex anchors to hook-on rails, concealed anchors and monocoque subframes, project teams can choose a solution that suits both the design intent and the realities of construction.
The most reliable results come from collaboration. Bringing the designer, the engineer, the fire consultant and the manufacturer together early, as ShapeShift Technologies does through its integrated approach from design and engineering to production and installation support, keeps the architect’s vision buildable and the risk low. If you are planning a fibre-reinforced facade, start the conversation about attachment on day one, not at shop drawings.
Further Reading
The following resources from ShapeShift Technologies expand on the topics in this guide:
