Hi - I have to install a pair of HSS steel tubes 7" tall, 2" wide through the side of an old building from the 20's that has sheet copper over wood backing. I am worried about the galvanic reaction if the steel and the copper touch and additionally, and more importantly, I wonder how to make the opening water proof?
I am worried, since the building's management is not big on maintenance, that caulking the gap may not be a good idea. Due to expansion and contraction with the seasons, it may fail over time. I was thinking of making a sort of flange from copper that could stick out a half an inch or so and be soldered to the copper skin and the gap between the tube and the copper flange could be filled with caulk.
Is that a sound approach or is there a better way?
Peel n stick flashing membrane will help achieve a separation between the two metals. The membrane would also help as a flashing detail. I'm not sure how this would work if you solder, perhaps if the flange is large enough the heat will be dispersed and not melt the membrane.
If you caulk, use something such as silicone which stays flexible. And if the gap is greater than 1/8" or so, use a backer rod.
JLC has articles on proper caulking which are worth a read.
So, the fire escape platform is steel also? And it will sit in the flange?