Fibre Reinforced Facade Encyclopedia: Design and detailing
A unitised facade is a curtain wall delivered to site as complete, factory-assembled units, usually one storey tall and one or two modules wide, which are lifted into place and hung from the slab edge on brackets. Each unit arrives glazed, gasketed and sealed, and the only site operation is landing it and letting it engage with the units already installed. It is called a unitized curtain wall in North America. The alternative is a stick system, where extruded mullions and transoms are fixed to the building one piece at a time and the glass and panels are installed into that grid on site.
A unitised unit leaves the factory as a finished piece of wall. A stick facade leaves the factory as a pile of aluminium sections and a crate of glass, and becomes a wall only after several weeks of work at height.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Unit size | Typically 1.2 to 1.8 m wide by one storey tall | Floor to floor height, commonly 3.0 to 4.2 m |
| Unit weight | 250 to 800 kg typical | Depends on glass make-up, spandrel and any moulded panel |
| Support | Hung from the slab edge on two brackets per unit | Dead load to one level, wind load in and out |
| Unit to unit joint | Split mullion and split transom | Two half sections interlock, gaskets seal, no site sealant |
| Joint design | Pressure equalised, drained and vented at each unit | Water collected in the mullion and taken out at the stack joint |
| Stick system | Assembled and glazed in place | Lower tooling cost, longer programme, site sealed joints |
How a unit is hung and how units join
Each unit carries two brackets that engage a slab edge anchor, usually a cast-in channel or a post-fixed anchor plate, with adjustment in three axes so the unit can be set plumb and level against real structural tolerances. The unit hangs from one floor only. It is restrained against wind load in and out at the same level, and it is deliberately not restrained at the floor above, so that slab deflection, creep, shortening and inter-storey drift are not transferred into the facade.
The joint between units is the defining detail. Every vertical mullion is split lengthways into two halves, one on each adjacent unit, so that when the second unit is landed the two halves interlock. The same is done horizontally at the stack joint. The interlock carries no load; it locates the units and holds the gaskets. Three lines of gasket are typical: an outer rain deflection line, an air seal at the back, and a drained and pressure equalised chamber between them. Water that gets past the outer line runs down the mullion cavity, meets the stack joint, and is taken out to the face through a controlled path. Nothing depends on a bead of site applied sealant, which is the single largest difference in long-term performance between unitised and stick facades.
The programme and quality argument
Unitising moves work off the critical path and off the building. A unit is assembled on a bench in a factory, at a comfortable height, under cover, with jigs, repeatable torque and consistent sealant cure conditions, and it can be tested before it ships. A stick facade is assembled on a swing stage or a mast climber, at height, in whatever conditions the day offers. The quality difference is not about skill; it is about the conditions the work is done in.
On programme, a unitised facade starts as soon as the structure is high enough to hang from, and follows the structure up floor by floor. The building becomes weathertight much earlier, which lets internal trades start, which is usually where the real saving sits. Against that, unitised systems carry higher tooling, engineering and mock-up cost up front, need design to be frozen much earlier, and leave almost no room for change once units are in production. Stick systems remain the sensible choice for low rise work, small areas, irregular one-off geometry and projects where the design is still moving.
Crane, hoist and handling
Units are large, heavy and fragile, and how they get to their position governs the whole installation method. On a tall building the tower crane is usually the structure’s, not the facade’s, so units are typically raised by a monorail and trolley fixed to the slab above, by a davit or monorail at roof level with a mini crane, or by a material hoist to the working floor and then moved horizontally on a trolley. Each of these sets a hard limit on unit weight, which is one of the first numbers agreed in a facade package.
- Unit weight limited by the hoisting method, not by structure
- Transport: units are shipped in stillages, and stillage size fixes the maximum unit dimension long before the crane does
- Access: once units are in, there is no scaffold, so any remedial work needs a BMU or rope access
Where a moulded panel fits
A glass fibre reinforced concrete (GRC, GFRC) or fibre reinforced polymer panel does not replace a unitised system; it becomes part of one. The panel is fixed to the unit frame in the factory, most often as the spandrel, as a projecting fin or blade, or as a shaped infill in place of an opaque metal panel. It arrives on the building already aligned to the unit, already sealed to it, and already checked.
Three things have to be agreed early. Weight, because the panel adds directly to the unit weight and therefore to the hoist limit; a GRC spandrel at 30 to 50 kg per square metre is not a large addition, but a deep three dimensional element can be. Fixing, because the panel needs its own gravity and flex anchor arrangement back to a frame that is aluminium rather than steel. And movement, because the panel expands at a different rate from that aluminium, so the connection has to allow it rather than restrain it.
Standards and references
- AS 4284 Testing of building facades: static and cyclic water penetration, air infiltration, structural and serviceability testing
- AS/NZS 1170.2 wind actions; AS/NZS 1170.0 for design working life and serviceability
- CWCT Standard for Systemised Building Envelopes (United Kingdom)
- AAMA 501 series, ASTM E283, E331 and E1105 (United States curtain wall testing)
- NCC 2022 Volume One, external wall and vertical separation provisions (check the edition adopted in your jurisdiction)
- AS 1530.1 and AS 5113 for the reaction to fire position of the facade system
Where this matters on a ShapeShift project
One Sydney Harbour, Barangaroo: A high rise residential tower where moulded panels form part of a factory-assembled facade, delivered to the building as finished elements rather than assembled at height.
Related terms
Questions specifiers ask
What is the difference between unitised and stick curtain wall?
A unitised facade is assembled and glazed in a factory and delivered as complete storey-height units. A stick facade is delivered as separate mullions, transoms and glass and assembled in place on the building.
How are unitised facade units supported?
Each unit hangs from two brackets on one slab edge, with three-way adjustment. It is restrained against wind at that level and is deliberately not restrained at the floor above, so structural movement is not transferred into the facade.
What is a split mullion?
A vertical mullion divided lengthways into two halves, one on each adjacent unit. When the next unit is landed the halves interlock and the gaskets between them form the weather seal, with a drained and pressure equalised chamber between the outer and inner lines.
Can GFRC or FRP panels be used in a unitised facade?
Yes. The panel is fixed to the unit frame in the factory and delivered as part of the unit. Agree the added weight against the hoist limit, the anchor arrangement into an aluminium frame, and the differential movement between the panel and the frame.
Integrating a moulded panel into a unitised facade? ShapeShift engineers panel connections to unit frames and delivers panels to the unitiser rather than to site. Talk to our facade engineers
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.