I bought a 1920's semi 4 years ago. The survey reported that the wall ties needed replacing so a local firm was hired to do this. Now it has come to redo the rendering and I have received conflicting info. I have been told that the old wall ties should have been removed when the new ones were fitted as they will continue corroding, but have also been told that as a flexible, silicone render is going to be applied that they don't matter as the render will expand. Who do I believe?