Window Trimmers

Window Trimmers

Used in conjunction with C-section side rails, C-section window trimmers provide the necessary surface fixings for windows, claddings and associated flashings.

The window trimmer should ideally be of the same depth as the main supporting rail and be connected using riveted C-rail (RCR). Counterformed holes provide the necessary unobstructed fixing surface.

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Riveted C-rails

Riveted C-rails up to 2.5m long are delivered to site with pre-fixed end cleats to aid in the speed of erection and avoid the possibility of losing loose cleats.


Complex arrangement of windows within a wall elevation illustrating how each bank of windows requires a system of diagonal tie wire bracings in combination with RCR’s.

Detail 1

NB: All side rail systems are generally designed to a vertical deflection limit of Span/300. However, if a more stringent deflection limit is required by the cladding contractor, e.g. over window openings, then please contact our technical department for advice.

Detail 1 – jamb and vertical strut connection

Detail 2

Pre-fixed cleats on lengths up to 2.5m

Section A-A

Window trimmer detail 2

For lengths over 2.5m bolted end cleats are required