When the previous construction was done, the workers already installed steel beams, corregated steel and a drain for this future conversion project. So this job basically requires the current roof to be pulled off, waterproofing done and then concrete poured. Additionally, the current window will be converted into a door for terrace access.

This brings me to the question in hand. Since most of this future terrace is situated above our kitchen, we want to make sure that we do proper and long-lasting waterproofing. My research has led me that proper flashing needs to be done. The question is this: Should I use copper (more expensive) or aluminum should work just fine? Are there any other suggestions?

My main goal is that we want to use something that will last a long time. We plan to put tile as our walking surface of the terrace.

Thanks!

Aluminum touching any cement products get eaten in short order.