I purchased a home that was a two family converted to single. Brick veneer on the outside and block inside. I have been assured by two structural engineers that I have no foundational issues. I have a gap developing between the staircase and the wall. The previous owner just lazily sealed the gap with caulking which as shrunk and pulled apart. So I went through with a flat blade and started peeling the caulking off between the staircase and the wall. In some places, there's almost an inch gap. The block can be seen underneath the plaster. What is the best thing to use to help close the gap?