Concrete structures are typically built to tolerances of +-15 to 20mm. The finished facade needs to read as flat and plumb to within +-2 to 3mm. Bridging that gap - consistently, across every floor and every elevation - is one of the most practically important coordination tasks on any facade project. Get it wrong and you end up with visible waviness, misaligned joints, or panels that simply do not fit.
Where does the tolerance get absorbed?
The subframe and bracket system is the tolerance absorption layer. It sits between the as-built structure and the finished cladding plane, and its job is to reconcile the two. Adjustable brackets allow the installer to set each fixing point to the correct position relative to a surveyed datum, compensating for slab-to-slab level variation, column plumb deviations, and slab edge irregularities.
Without adequate adjustment range in the brackets, the installer has no way to correct for structural variance. The facade either follows the imperfections of the structure - producing a wavy, out-of-plumb result - or the panels cannot be installed at all because the fixings do not reach or the clearances are consumed.
What types of tolerance are in play?
Three categories of tolerance converge on every facade installation, and they are largely independent of each other.
Structural tolerances. These are the as-built deviations in the primary structure - slab level, slab edge position, column plumb, and beam soffit level. Australian standards permit concrete construction tolerances in the range of +-10 to 20mm depending on the element and the class of finish. In practice, some areas of a building will be close to nominal and others will be at or beyond the permitted limits.
Manufacturing tolerances. These are the dimensional variations in the facade components themselves. For element13 solid aluminium panels, manufacturing tolerances are tightly controlled: width +-2.0mm (for panels over 1200mm and up to 1500mm wide), length +-4.0mm (for panels over 3000mm), and thickness +-0.18mm. interloQ extruded profiles are manufactured to AS/NZS 1866:1997 extrusion tolerances, which govern cross-sectional dimensions and straightness. These are small numbers - the manufacturing process is precise. The structure is not.
Installation tolerances. These are the achievable accuracy of the facade set-out and installation itself - plumb, level, flatness of the finished plane, and joint widths. Installation tolerances sit somewhere between structural and manufacturing. They depend on the quality of the survey, the adjustment range of the brackets, the skill of the installation crew, and the time allowed for the work.
How does 165CW handle structural variance?
Unitised curtain wall systems face this problem in a concentrated way because the units are factory-assembled to precise dimensions and then hung on a structure that is not precise. Valmond & Gibson’s 165CW unitised curtain wall addresses this with a 3-part structural bracket system that provides three-dimensional installation adjustment. The system accommodates +-25mm of stack head movement and +-10mm of mullion movement, giving the installer enough range to set each unit true regardless of slab-to-slab variation.
This is not a luxury feature - it is fundamental to how unitised curtain wall works. Without adequate bracket adjustment, the units cannot be aligned and the gaskets between units will not compress correctly, which compromises weather performance.
What goes wrong when tolerances are not managed?
The most common problems come from the same root cause: assuming the structure matches the design drawings.
Inadequate bracket adjustment range. If the brackets are designed for +-10mm of adjustment but the structure is out by 25mm in places, the installer runs out of room. Remediation typically means custom packers, re-engineered brackets, or accepting a compromised facade plane.
No structural survey. Ordering facade components and designing bracket layouts based on as-designed dimensions rather than as-built dimensions is a gamble. The further the structure deviates from design, the more expensive the rework.
Tight facades on loose structures. Specifying very tight joint tolerances on a building with significant structural deviation creates an impossible task for the installer. The joint tolerance must be achievable given the cumulative tolerance stack-up from structure through brackets to finished face.
What is the practical approach?
The rule is straightforward: survey the as-built structure before finalising the facade bracket design and before ordering materials.
A facade survey identifies the actual position of every slab edge, column face, and fixing zone relative to the theoretical design datum. From this data, you can calculate the worst-case deviations on each elevation and design the bracket system to cover the full range. You can also identify areas where the structure is so far out that it needs remediation before the facade goes on - grinding high spots, filling low spots, or accepting a locally adjusted facade line. The earlier this survey happens after the structure is complete, the more flexibility you have to respond.
Getting it right
Tolerance management is not glamorous work, but it is the difference between a facade that installs smoothly and one that generates weeks of delays and rework. A proper structural survey and an adequately adjustable bracket system pay for themselves many times over.
V&G can advise on bracket adjustment requirements for interloQ, element13, and 165CW systems. If you need to understand the tolerance absorption range for a specific system, contact us. We would rather help you get the details right upfront than troubleshoot fit problems on site.
Related Reading
- Coordination Between Facade and Structure: Common Clashes
- Subframe Design for Aluminium Rainscreen Cladding
- Measuring for Aluminium Cladding: Tolerances and Best Practice
- Thermal Expansion in Aluminium Facades: A Design Guide
Last updated: 4 April 2026