The decision about method belongs to the owners corporation
Cleaning agreements usually describe outcomes, which works perfectly well on modern surfaces where the route to the outcome barely matters to anyone. On an original tessellated entry or a soft sandstone step, the route is the entire question. An aggressive product removes the mark and takes something else away with it, and no amount of future service recovers what was lost in that one attendance.
Because those surfaces are common property, the owners corporation is both the party affected and the party that should be deciding. That is a practical observation rather than a legal one: the committee is who answers to owners if a finish is damaged, and no contractor can carry that conversation on their behalf. Putting proposed methods into the written scope and having them approved before mobilisation converts a silent risk into a recorded decision with a date on it.
