Omnia Flush Sash – Understanding Mullions & Transoms
One of the key design features of our Omnia Flush Sash Casement Window is its beautifully clean appearance.
As standard, Omnia has been designed with invisible external mullions and transoms, helping to create slimmer sightlines, a cleaner external finish and, importantly, more glass and more natural light.
Standard Mullions & Transoms – 62mm
Where a mullion or transom measures up to 1565mm in length (excluding outer frame, cills and add-ons), the standard 62mm mullion/transom can be used.
This remains invisible externally, maintaining the clean, flush appearance that makes Omnia so distinctive.
Over 1565mm – Structural Upgrade Required
Where an individual mullion or transom exceeds 1565mm in length, a structural upgrade to the heavier mullion/transom is required.
This upgraded section becomes visible externally and also increases the internal face dimension from:
62mm → 84mm
This adds 22mm to the internal sightline compared with the standard mullion/transom.
Why Does This Matter?
The upgrade isn’t simply a design choice. It is required to provide the additional structural strength needed for larger configurations.
Where sizes allow, the standard 62mm invisible external mullions and transoms give Omnia its particularly clean appearance, with less visible frame, more glass and more light.
IMPORTANT: When designing or ordering Omnia Flush Sash windows, please be aware that configurations exceeding the 1565mm mullion or transom limit will have a different appearance due to the required structural upgrade.