Hello all, my partner and I bought our first home last spring, and now that we have spent our 1 year anniversary in the home, we are ready to start the hard work. The home was built in 1875, and has been added on to who knows how many times. It is a 1 story home, with a half basement. We LOVE the high ceilings and the old home feel. But it certainly has some issues that need fixed. The walls are solid brick (3 thick I believe), but 3 of the outside walls have vinyl siding over the brick (previous owner did this). The interior side of one of those walls has plaster crumbling off. The plaster is applied directly to the brick. Now I have 2 questions:

1. Is the vinyl siding causing the water problem that is causing the plaster to crumble?

2. What is the best way to repair this? The majority of the wall is crumbling, and it is getting significantly worse.

Now I am a DIY guy and love to fix stuff. Therefore I would like to do the repair work myself. However, I am a complete lamen when it comes to home repairs, so please keep this in mind when giving advice Thank you.