Stick vs Unitised Curtain Walling: The Honest Comparison

The choice between stick and unitised curtain walling is one of the most consequential specification decisions on a commercial building. Get it right and the facade comes off the critical path. Get it wrong and you'll spend the programme chasing weathertightness on scaffold in November. This guide compares both systems on the metrics that actually move on a tender comparison.

What Each System Actually Is

Stick curtain walling is assembled on site: mullions are fixed first, transoms span between them, and IGUs are loaded into the grid and pressure-plated by installers working from internal access or external mast-climbers. Every component is delivered loose.

Unitised curtain walling arrives as factory-assembled, pre-glazed storey-height panels. Each unit is lifted into position by tower crane or material hoist, then locked into the panel below via a male/female interlocking stack joint with EPDM gaskets pre-installed. The full system is closed and weathertight as soon as the last unit on a floor is set.

Speed and Programme

Per team, per day: stick installs 25–45 m² of facade. Unitised installs 80–150 m². That's a 3–5× productivity multiplier. On a high-rise the difference is decisive — a 40-storey residential tower clad in stick can take 14–18 months; unitised brings that to 6–9 months.

Unitised also enables follow-on trades (M&E, fit-out, drylining) to start on lower floors weeks earlier because each floor goes weathertight as soon as its units are set. On stick, no floor is weathertight until every transom, gasket and pressure plate is sealed and tested — meaning fit-out routinely waits 4–8 weeks behind facade.

Quality Control

This is where unitised quietly wins. Factory assembly means glazing is bonded at 20°C and 50% RH on a clean bench, gaskets are compressed under calibrated torque, and every unit is water-tested before it leaves the factory. Defect rates on factory-glazed unitised typically run 0.2–0.8%.

Stick is glazed at 4am in the rain in February by an installer 30m up on a mast climber. Even with the best teams, in-situ defect rates run 2–5% and are far more likely to be discovered late, after pressure plates are capped and access is gone.

When Stick Wins

• —Refurbishment projects where existing structure tolerances are wide or unknown
• —Bespoke geometry — faceted, curved or one-off feature elevations
• —Low-rise (1–4 storeys) where crane time would be hard to justify
• —Heritage and conservation work where mullion profiles are non-standard
• —Schemes with no realistic factory lead time available

When Unitised Wins

• —Any building above 6 storeys
• —Repeating typical bays across multiple elevations
• —Tight programme — particularly weathertight-date driven
• —Constrained sites with no room for scaffold or external access
• —Schemes targeting BREEAM Excellent / NABERS — QC drives airtightness numbers
• —High-performance residential targeting Future Homes-equivalent envelope

The Honest Verdict

Most current UK commercial and residential projects above 5 storeys default to unitised, and rightly so. The right number to optimise against isn't the headline material premium — it's total facade-related programme delay plus rectification risk, and on that basis unitised wins 8 times out of 10.

Stick remains the right answer for refurbishment, low-rise, bespoke geometry and short-lead programmes where there's simply no time to put units through a factory. Treat the choice as a project-specific question, not a default.

Frequently Asked Questions