Stick Or Unitised Curtain Walling For Multi-Storey Buildings

Selecting a curtain wall system for a multi-storey block affects programme, cost, appearance, thermal performance and long-term maintenance. Stick-built and unitised curtain walling can both deliver high-quality glazed façades, but they suit different project conditions. The right decision depends on the building’s geometry, access, repetition, procurement route and performance requirements.

For Australian developments, the choice must also respond to local wind loads, solar exposure, bushfire considerations in some locations and the requirements of the National Construction Code (NCC). A residential tower in Melbourne may have very different façade priorities from an apartment project in Brisbane, Perth or coastal New South Wales.

Stick systems are assembled on site from mullions, transoms, glass and spandrel panels. Unitised systems arrive as factory-built panels, generally incorporating framing, glazing, insulation, gaskets and sometimes external finishes. This fundamental difference influences how much work takes place at ground level or on the building elevation.

Early coordination between the façade contractor, architect, structural engineer, services team and main contractor is essential. A specialist contractor can help test the buildability of each option before the design is locked, as explained through this guidance on early facade input.

How The Two Systems Are Built

Stick curtain walling is delivered as a collection of individual components. Vertical mullions are fixed to slab edges or brackets, horizontal transoms are installed between them, and glazing or opaque infill panels are fitted afterwards. Seals, pressure plates, cover caps and flashings complete the weather-resistant assembly.

This approach gives installers considerable flexibility. Variations in floor-to-floor height, bay width and window position can often be accommodated on site without redesigning an entire panel. It can be particularly useful for smaller buildings, podiums, complex interfaces or projects where the façade changes frequently from one elevation to another.

Unitised curtain walling is manufactured in panels that typically span one storey and one structural bay. Glass, spandrel zones, insulation, opening vents and internal finishes may be integrated before delivery. Panels are then lifted to the required level and connected to adjacent units through engineered joints.

The factory environment provides greater control over assembly tolerances and sealant application. However, unitised construction depends on accurate structural dimensions and a carefully coordinated grid. Once production begins, changes to mullion positions, slab edges or window modules can have substantial cost and programme consequences.

Programme And Site Conditions

A major advantage of unitised façades is the potential for rapid installation. Panels can be delivered in sequence, lifted using a hoist or crane and fixed from inside the building or from a limited amount of external access equipment. This can reduce the number of trades working on the elevation at the same time.

That benefit is valuable on high-rise projects in dense Australian locations. A Sydney or Melbourne site may have restricted street access, limited laydown space and strict delivery windows. Factory-produced panels can reduce wet trades and repetitive façade work at the edge, although transport planning and just-in-time logistics become critical.

Stick systems generally require more activity on the building face. Mullions, transoms, glass and pressure plates must be handled and installed in stages, often using mast climbers, suspended platforms or perimeter screens. The sequence can be slower on a tall tower, particularly when wind interrupts lifting or external access.

The practical site question is not simply which system installs faster in theory. It is whether the project has enough crane time, storage, edge protection, skilled installers and weather windows to support the chosen method. On a tight programme, a unitised façade may protect the critical path; on a smaller site, the manufacturing and transport demands may outweigh that advantage.

Design Freedom And Appearance

Stick curtain walling offers broad design adaptability. Different glass sizes, transom positions, feature fins, projecting frames and changes in bay rhythm can be introduced without creating a completely new panel family. This makes it suitable for façades with irregular geometry or a strong relationship between glazing and adjacent cladding.

It can also support late-stage design development more readily. If an architect refines a podium entrance, adjusts a spandrel zone or responds to planning feedback, a stick system may absorb the change with fewer manufacturing implications. The trade-off is that more workmanship takes place on site, so installation quality and inspection procedures are especially important.

Unitised curtain walling is strongest where the elevation follows a repeatable module. Regular apartment towers, student accommodation, hotels and commercial buildings can benefit from a consistent panel design and controlled joint arrangement. Factory glazing can provide a clean finish, while integrated spandrel panels allow the external elevation to combine vision glass, opaque glass and rainscreen elements.

The system does not have to look repetitive, but visual variety requires careful engineering. Different panel types, corner units, parapet conditions and transfer zones can be manufactured, yet each additional variation affects tooling, quality checks, packaging and installation sequencing. A façade engineer and specialist contractor should review the architectural intent against the proposed panel matrix early.

Performance, Compliance And Durability

Both systems can meet demanding requirements for air permeability, water penetration, wind resistance, thermal insulation and acoustic control when correctly designed and installed. The key is the complete façade build-up rather than the frame alone. Glass specification, thermal breaks, spandrel insulation, slab edge treatment, cavity barriers and interfaces with roofing or cladding all influence performance.

Australian projects need assessment against the NCC and relevant Australian Standards, including requirements related to structural adequacy, glazing safety, energy efficiency and weatherproofing. Wind conditions vary significantly between locations, and exposed coastal sites can create additional corrosion and durability concerns. A façade solution suitable for an inland Melbourne block may need different finishes, fixings or detailing in Brisbane or a cyclone-prone region.

Unitised façades can provide strong repeatability because joints, gaskets and panel components are tested under controlled conditions. However, the movement strategy must be carefully designed. Building sway, differential slab movement, manufacturing tolerances and thermal expansion are managed through interlocking unit joints and adjustable anchors.

Stick curtain walling can also accommodate movement effectively, but its numerous field joints demand disciplined installation and inspection. Drainage paths must remain clear, pressure plates must be correctly fixed and sealants must be compatible with adjacent materials. Mock-ups and performance testing are useful for either approach, especially where the building has demanding acoustic or water-management targets.

Cost, Procurement And Risk

Comparing headline supply rates can give a misleading picture. Stick curtain walling may have lower initial fabrication costs, but site labour, access equipment, protection, storage and longer installation periods can increase the total installed price. Unitised curtain walling may carry higher factory and design costs while reducing elevation labour and shortening the enclosure programme.

The commercial balance depends on repetition and scale. A large tower with hundreds of similar panels may justify dedicated production, specialised transport frames and detailed factory testing. A low-rise apartment building with numerous corners, balconies and changing openings may achieve better value with a stick-built solution or a hybrid façade.

Procurement strategy also matters. A design-and-construct project can benefit from early contractor involvement, allowing the façade package to be coordinated with slab tolerances, fire stopping, windows, balconies and building services. A fully developed traditional procurement model may offer more design certainty, but it can leave less opportunity to adjust the system when fabrication constraints become clear.

Risk allocation should be explicit in the subcontract. Responsibilities for surveys, setting out, structural movement, performance testing, replacement glass, storage damage and interface sealing need to be defined. Clear responsibility is particularly important where the curtain wall meets precast concrete, metal cladding, roof membranes or architectural glazing.

Choosing For The Building And The Market

Stick curtain walling is often the practical choice when a project has modest repetition, irregular geometry, changing bay sizes or limited factory lead time. It can suit refurbishments and extensions because installers can respond to existing conditions as they are exposed. It may also be appropriate where local access is straightforward and the programme has enough float for progressive installation.

Unitised curtain walling is generally compelling for tall, repetitive buildings where speed, consistent quality and reduced external work are priorities. It can help enclose floors quickly, allowing internal trades to start earlier. For a major apartment or commercial development in a congested CBD, that programme benefit may be worth the additional design management and logistics planning.

A hybrid strategy can be effective. A project may use unitised panels across the repetitive tower, stick curtain walling at the podium and bespoke architectural glazing at entrances or winter gardens. This approach matches the construction method to each elevation rather than forcing one system across the entire building.

Past project experience can help assess how a contractor manages complex interfaces, panel sequencing and visual quality; the Media City project provides a useful example of façade delivery in a demanding built environment. For Australian clients, comparable experience should be tested against local compliance, climate, supply chains and site constraints rather than judged on appearance alone.

Planning The Decision Early

The decision should begin with a performance brief. Establish the required U-values, solar control, acoustic targets, fire strategy, wind pressures, drainage approach, maintenance access and expected service life before comparing quotations. A façade contractor can then price systems on a consistent basis instead of offering a nominal square-metre rate with major exclusions.

The design team should also prepare a realistic façade grid. This includes floor-to-floor dimensions, slab edge tolerances, corner conditions, parapets, balcony interfaces, movement joints and areas where cladding changes material. The more accurately these conditions are understood, the easier it becomes to identify whether panelisation or site assembly is better suited.

Mock-ups should address appearance and performance. They can reveal colour variation, glass reflectivity, gasket visibility, shadow lines and junctions with adjacent materials. Performance testing can identify water leaks or movement problems before the same detail is repeated across hundreds of bays.

The strongest choice is the one that balances construction speed, design intent, compliance, durability and whole-life value. For a multi-storey block, curtain walling is part of an integrated building envelope, so its success depends on coordinated detailing, capable installation and clear accountability from design through handover.