Referring to the photo above, I have this detail on my project where the engineer is insisting on structural steel (highlighted in blue) to support a lighting element (highlighted in yellow). The lighting element is 125 feet long and weighs 1.5 pounds per foot. The flashing shown over the top of the steel angle is part of my waterproofing system and is .040 aluminum that is doubled up with a hemmed edge.
They're calling for this support angle to be a 7x4x3/8. The attachment of the angle makes it a costly detail to construct (not shown in bid documents) and it is difficult to properly waterproof the facade with this angle attached to the building.
I think I could fabricate a cold formed steel angle to reinforce the aluminum angle at a significantly lower cost and it wouldn't fowl up my waterproofing system. If so, how thick should that angle be (18ga, 16ga, thinner or thicker?)
Show your work because I'll need to convince the engineer.