Different methods of mullion support


This picture shows a base curtain wall anchor installed on 9 steel shims few weeks before the photo was taken. There is no systemic method of anchor adjustment. The design called for shims "as required." Both shims and anchor are already heavily rusted, probably as a result of galvanic action (no electrical separation was provided between steel and aluminum). Rust will expand up to 10 times within each of the 10 joints. Expanding rust will exert an upward pressure and may lift the curtain wall mullion. Coincidentally, some vertical mullions of this two-story high curtain wall are incorrectly fixed at the top, although the design calls for sliding anchors that would allow for slab deflection. Excessive stress build-up in adjacent glass lites may cause glass breakages resulting in unsafe conditions.

Photo below shows a base anchor of other mullion of the same curtain wall. The base concrete curb is 5 inches short. The designer did not specify any method of anchor adjustment. It's explains the importance of analysing envelopes of tolerance for all rough building elements like cast-in concrete and movement envelopes for all moving components in the design phase..


Photo below shows base anchor of other mullion of the same curtain wall. Base anchor plate was welded to the top of vertical rebar embedded in concrete, but it's a challenge to pour concrete under a continuous plate,; therefore a gap was created. The rebar already is covered with delaminating rust.