How Is a Curtain Wall Installed?

Everything depends on a survey carried out before a single bracket goes up.

Concrete frames are not built to the tolerances a facade needs. A slab edge can wander by 25 mm or more against the design line across a floor plate, and the curtain wall has to sit in a straight plane regardless. Anchors accommodate that deviation, but only if somebody measured it first and ordered the right adjustment range.

Crews who skip the survey discover the problem floor by floor, with brackets that will not reach, packing shims stacked beyond what the engineer allowed, and a facade line that visibly bends when you sight along it from the corner.

This article covers the sequence properly, for both construction methods. PRANCE provides installation guidance and reference details for the systems we supply.

Stick and Unitized: Two Different Installation Methods

The choice is made at design stage and it changes everything about how the facade reaches the building.

Stick Curtain Wall Installation

Components arrive as individual pieces. Mullions, transoms, glazing, gaskets, and pressure plates are all assembled in position on the building.

Mullions go up first, anchored at slab level and spanning vertically. Transoms fit between them. Glazing is then set into the frame from outside, usually requiring external access, and pressure plates and cover caps secure it.

More site labor, more weather exposure, more opportunity for workmanship variation. The advantages are lower tooling cost, easier accommodation of irregular geometry, and simpler logistics, since components stack compactly.

Stick systems suit low and mid-rise buildings, complex geometry, and projects where site access permits external working.

Unitized Curtain Wall Installation Sequence

Factory-assembled panels arrive complete. One storey tall, one or two bays wide, with glazing, gaskets, and insulation already installed.

Each unit is lifted into position and engaged with the unit below and beside it. The interlocking male and female profiles at the panel edges form the weather seal as the units mate, so sealing happens through engagement rather than through site-applied sealant.

Faster erection, better quality control since assembly happens in a controlled factory, and far less external access required because units are typically installed from inside the slab edge.

The costs are higher tooling, tighter tolerance requirements, larger transport and crane demands, and almost no flexibility once units are fabricated. How the units arrive on site covers the fabrication side.

Survey and Setting Out

The stage that determines whether everything downstream works.

As-Built Survey

The structure is measured as it exists, not as it was drawn. Slab edge position, slab level, floor-to-floor heights, column positions, and any deviation from the design grid.

Total station survey is standard. On renovation work or complex geometry, 3D laser scanning produces a point cloud that captures conditions no tape measure would find, which is worth the cost where the existing structure is uncertain.

Establishing the Facade Line

A primary control line is established, usually offset from the structure, and every anchor position references it.

Vertical control uses a plumb line or laser down the building face. Horizontal control works from floor datum levels. Both are checked independently rather than taken from the structural setting out, since the structure itself carries deviation.

Tolerance Reconciliation

The survey is compared against the anchor adjustment range. Where deviation exceeds what the standard anchor accommodates, the options are modified brackets, structural correction, or a revised facade line.

Finding that at survey stage is a design conversation. Finding it during erection is a programme problem.

Anchor Installation

Anchors transfer wind load and dead load from the facade into the structure, and they carry the adjustment that reconciles facade geometry with structural reality.

Typical adjustment ranges allow movement in three axes, commonly in the order of plus or minus 25 mm vertically and horizontally, with slotted holes or serrated plates locking the final position.

Key points at this stage:

• Anchor type matched to the structure, whether cast-in channel, post-fixed anchor, or welded plate

• Edge distance and embedment verified against the structural engineer's requirements

• Corrosion protection appropriate to exposure, with stainless or hot-dip galvanized fixings where conditions demand

• Thermal isolation where the anchor crosses the insulation line, using structural thermal break pads

• Torque verification and recorded sign-off before loading

Post-fixed anchors into concrete frequently require pull-out testing on a sample basis, particularly where the concrete strength is uncertain.

Erection Sequence

The order differs between methods, though the principles hold for both.

Deliver and stage. Units or components delivered in erection sequence, which matters enormously on constrained sites with no storage.

Set the first unit. The reference unit, positioned against the control lines and checked in all three axes before anything else engages with it.

Work from the bottom up. Each course sits on the one below. Errors accumulate upward, which is why the first course gets disproportionate attention.

Check alignment continuously. Every few bays rather than every few floors. A 2 mm drift per unit becomes 40 mm over twenty units.

Install movement joints as designed. Stack joints between units accommodate live load deflection and thermal movement, and closing them up during erection causes problems later.

Seal perimeters. Head, sill, and jamb conditions where the facade meets structure, using backing rod and sealant rather than foam alone.

Protect installed work. Facade damage from following trades is a routine and avoidable cost.

Tolerances

Industry practice commonly works to approximately 3 mm maximum deviation from plumb over one storey, and 12 mm over the building height, with alignment between adjacent units typically held within 1.5 mm.

Those are tighter than structural tolerances, which is exactly why anchor adjustment exists.

Installing in Difficult Conditions

Two conditions that change the method rather than just slowing it.

Cold weather. Sealants have minimum application temperatures, typically around 5 degrees Celsius, and curing slows considerably below that. Surfaces must be dry and frost-free. Sequencing in freezing conditions is a planning problem as much as a technical one.

Wind. Lifting operations have wind speed limits, commonly around 10 m/s for panel handling depending on panel size and crane type. On tall buildings this can make erection weather-dependent for weeks at a time, which belongs in the programme rather than being discovered.

Curtain Wall Installation Checklist

A practical sequence of verification points.

• Before start: as-built survey complete, control lines established, tolerance reconciliation signed off

• Anchors: type verified, embedment checked, pull-out tested where required, torque recorded

• First unit: position checked in three axes, independently verified

• Each course: alignment, plumb, and level checked and recorded

• Joints: stack joints at designed dimension, gaskets correctly seated, no twisted or pinched seals

• Drainage: weep holes clear and unobstructed by sealant or debris

• Perimeter seals: backing rod sized correctly, sealant tooled, no gaps at corners

• Testing: field water test on early bays per AAMA 501.2 or ASTM E1105

• Protection: installed facade protected from following trades

• Records: survey data, anchor sign-offs, and alignment checks retained for handover

Performance testing before and after erection explains why the field test belongs early rather than at completion.

Why Installation Quality Decides Facade Performance？

A system that passed every laboratory test can still leak, and the reasons are almost always the same handful.

Gaskets twisted or pinched during unit engagement. Corner seals missed where three planes meet. Weep holes blocked by sealant applied with good intentions. Stack joints closed up tight, so thermal movement has nowhere to go and the gasket is overcompressed. Perimeter seals installed against damp or dusty substrate.

None of those is a design fault. All of them are found by field testing early and corrected by changing how the crew works, which is the entire argument for testing the first bays rather than the last.

The labor share of a facade package is substantial, and installation quality is where that money either buys performance or does not.

Frequently Asked Questions

1. What is the difference between stick and unitized curtain wall installation?

Stick systems arrive as individual components assembled in position on the building, with glazing set from outside. Unitized systems arrive as factory-assembled storey-height panels that interlock with each other, erected faster and usually from inside the slab edge with far less external access required.

2. Why is a survey needed before curtain wall installation?

Because structural frames are not built to facade tolerances. Slab edges commonly deviate 25 mm or more from the design line, and anchors must be selected with enough adjustment range to reconcile that. Discovering the deviation during erection is a programme problem rather than a design conversation.

3. How accurate does curtain wall installation need to be?

Industry practice commonly works to approximately 3 mm maximum deviation from plumb over one storey and 12 mm over the full building height, with adjacent unit alignment typically within 1.5 mm. These are considerably tighter than structural tolerances.

4. Can curtain walls be installed in cold weather?

Yes, with planning. Sealants have minimum application temperatures around 5 degrees Celsius and cure slowly below that, surfaces must be dry and frost-free, and lifting operations have wind limits. Cold-climate programmes should sequence sealant-dependent work accordingly rather than assuming continuous progress.

5. When should field water testing happen during installation?

On the first installed bays, early in the erection programme. A workmanship problem found after a few bays can be corrected across the rest of the facade. The same problem found at practical completion is far more disruptive and expensive to remediate.

Getting Installation Right

Survey first, reconcile the tolerances before ordering anchors, set the first unit with disproportionate care, and check alignment continuously rather than periodically. Then test early, on real installed bays, while the crew still has most of the facade ahead of them.

The design work is already done by this point. Installation decides whether any of it reaches the finished building.

PRANCE manufactures stick and unitized curtain wall systems with as-built survey support, 3D scanning for complex and renovation work, coordinated shop drawings, and installation guidance. Send your structural drawings and programme and request installation support.