I'm mainly an interior GC. One of my best clients owns a 5 story apartment building in NYC. On one side of the building there is a party wall through which moisture is infiltrating. As far as he knows, the history of the wall is that 25 years ago, the entire wall was given a trowel coat. After perhaps ten years the moisture problem returned and he was (poorly) advised to have it painted with Thoroseal and he hired a contractor to do that about eight years ago.
The Thoroseal is now coming off in many places, but it's still probably 80% covered.
On his behalf, I have brought in a few waterproofing specialists and have basically been given two solutions. Before I mention the solutions I should say that I have been told that party wall bricks which were never expected to be exposed to the elements are an inferior grade of brick. Whether this is true or not, I don't know although it would certainly make sense. The building that was next to it was torn down decades ago.
One guy suggests attaching steel mesh to the surface and applying a coat of stucco.
The second guy told me there are two problems with this solution. Firstly, the nail gun that will likely be used damages the bricks as well as the mortar and he says inevitably the stucco will begin to pull away from the wall over time. He recommends taking off the existing Thoroseal and stucco down to the brick and then troweling on a slurry coat and repointing as needed.
As it seems to me that his solution was basically tried (with the initial trowel coat of stucco) I'm unconvinced that this will solve it. I want to get the right solution for this client that will last for many years. I figured I should come straight to the pros and get your opinions. Many thanks.