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What Is a uPVC Window Mullion?

What Is a uPVC Window Mullion? — here's a clear, practical explanation.

What a mullion is

A mullion is the vertical bar that divides a window into sections — for example, separating two sashes or a fixed pane from an opening one. Transoms are the horizontal equivalent.

What to know

Look for this

  • Vertical divider between window sections
  • Adds structure to larger windows
  • Separates fixed and opening panes
  • Reinforced for larger spans
  • Transom is the horizontal version

Why it matters for your windows

Mullions and transoms let larger or combination windows be built strong and stable — dividing big openings into manageable, well-supported sections.

Questions

Frequently asked

What Is a uPVC Window Mullion?

A mullion is the vertical bar that divides a window into sections — for example, separating two sashes or a fixed pane from an opening one. Transoms are the horizontal equivalent.

Does this affect window quality?

Mullions and transoms let larger or combination windows be built strong and stable — dividing big openings into manageable, well-supported sections.

Does Glassterr handle this?

Yes — we build and fit windows in-house at our Pannimadai factory, controlling these details.

From our range

What we make

uPVC Sliding Windows

Multi-track windows that need no swing space.

uPVC Casement Windows

Side-hung sashes for full airflow and the tightest seal.

uPVC Performance Systems

Double-glazed acoustic and thermal windows.

Related Guides

You might also need

Related guides covering this topic from other angles — different products, applications, or contexts.

Talk to the maker, not a middleman

Tell us your openings and we'll measure on site, advise, and give you a real quote — factory-direct from our Pannimadai works in Coimbatore.