Units can be combined with single units in single frames, which is called "box-to-box assembly." VistaLuxe® Collection WD LINE and Forgent Series products are all built with box-to-box assembly.Alternatively, several sash can be combined in a single frame, which is called "continuous sill assembly." All Ultra and Heritage Series casement and awning units now have continuous sill assembly, regardless of the sash widths or number of sash in the unit – up to 144 inches wide.

Ultra & Heritage Series Casement Mull Examples

Ultra & Heritage Series Awning Mull Examples

Size Limitations for Mulled Window & Door Units

Ultra and Heritage Series mulled units cannot exceed 168" (14 feet) x 108" (9 feet) overall. Larger sized mull unit assemblies may be possible, but require alternate installation methods or field mulling. The glass ratio cannot exceed 6:1 for annealed glass or 8:1 for tempered glass. VistaLuxe Collection WD LINE mulled units cannot exceed 120" (10 feet) x 96" (8 feet) overall.

^{NOTES: Large assemblies may be knocked-down by the factory for shipping and/or may need to be designed with structural reinforcement.Rough openings and opening dimension calculations are available on the Rough Opening Statement page.}