FAQ Knowledge Articles

French Casement units cannot be direct mulled. The only mulling allowed for French Casement units is when the operating unit is below, set directly on the rough opening framing, and a stationary (including stationary French Casement) unit is above.  This will require at least Mullion Reinforcement (MRF) or greater horizontal structure.  No mulling is recommended along side French Casement units.

For more information, see:
Marvin Ultimate French Casement
What kind of mulling does Marvin offer?