How do you strip failing parging before a recoat?

Loose and failing parging is chipped back with a hammer and chisel or a grinder until only sound, well-bonded material remains. In most repairs that means removing the damaged sections, not the whole wall. We tap the surface to find hollow areas, because the debonded zone behind a crack or flake is often larger than what you can see. Edges are cut clean so the new coat has something solid to lock against, and the exposed wall is cleaned of dust, paint and mineral residue. Parging directly over failing material traps the problem underneath, and the new coat usually comes off with the old one within a season or two. When most of the coat has let go, stripping the full wall and recoating is the better value. See parging recoating for how full recoats are done.