Unitized Curtain Wall: How It Works and When to Choose It
A unitized curtain wall is a glazed facade delivered as complete factory-assembled panels — glass already set into its frame — which are lifted into place and locked to the building floor by floor, rather than being built up from separate components on site.
By Dhruv Agarwal · · 2 min read
Why it matters on a facade project
The choice between unitized and stick-built is made early, usually before the facade contractor is appointed — and it is very hard to reverse. It sets the programme, the crane strategy, whether the building needs facade scaffolding at all, and how much of the work happens under factory conditions rather than at height in monsoon weather.
On a tall building it is often the single biggest determinant of how long the facade takes.
How it is specified in practice
| Parameter | Typical position | Why |
|---|---|---|
| Panel size | One floor high, one to two modules wide | Panel spans slab to slab so it can be installed floor by floor |
| Assembly | Complete in factory, glass already glazed | Controlled conditions; no site glazing at height |
| Joint type | Interlocking male/female stack joint | Accommodates building movement and drains water |
| Water management | Pressure-equalised, drained and vented cavity | Manages water that gets past the outer seal rather than trying to seal it out |
| Installation | Crane or monorail hoist, floor by floor | Removes the need for full-height facade scaffolding |
| Site labour | Low, but highly skilled | Setting-out tolerance is unforgiving once panels start stacking |
Common mistakes
- Comparing rate per square metre instead of delivered cost. Unitized looks more expensive on a BOQ line. It is often cheaper once scaffolding, site labour, rework and programme are counted.
- Underestimating setting-out tolerance. Panels interlock, so an error in the first row propagates all the way up. The brackets and the slab edge survey matter more here than on any other system.
- Ordering before the mock-up is tested. Once production starts, a design change means re-tooling. Air and water testing to ASTM E283 / E331 on a visual mock-up should gate the production release, not follow it.
- Ignoring crane availability. A unitized programme assumes lifting capacity when the panels arrive. If the crane is committed to structure, the facade waits and the whole benefit evaporates.
- Treating it as a tall-building-only system. It also suits fast-track low-rise work where programme matters more than rate.
When stick-built is the better answer
Unitized is not automatically superior. Stick-built remains the right choice on low-rise buildings, on facades with highly irregular geometry where few panels repeat, on projects where the design is still changing, and where the site has no crane access. Repetition is what makes unitized economical — without it, the factory tooling has nothing to amortise against.
Standards referenced
Wind loading follows IS 875 (Part 3), which sets the design pressure each panel and its brackets must resist. Air infiltration and water penetration performance is verified against ASTM E283 and ASTM E331 on a visual mock-up before production release.
Standards referenced
- IS 875 (Part 3) — Wind loads on buildings (Bureau of Indian Standards)
- ASTM E283 / E331 — Air infiltration and water penetration (ASTM International)
Frequently asked
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