A waterline on drywall does not by itself settle whether the board can be saved. The source of water, how long it stayed wet, the condition of the wall and what is behind it all matter.
Ask for a material-specific assessment rather than a universal rule. The right answer for a small fresh leak may be wrong after a sewer backup or long-hidden roof leak.
The water source changes the decision
Drywall exposed to sewage or contaminated floodwater may call for removal and special precautions even if the surface looks intact. A clean supply-line leak discovered quickly can be a different case, but its path through insulation and cavities still needs checking. Ask the assessor to explain how water entered and how far it traveled.
Look beyond the painted surface
Gypsum board can wick moisture above the visible line. Baseboards, insulation and the bottom plate may stay wet when the room-facing side feels dry. Moisture tools and selective inspection can help define the affected area. Ask what readings were collected and whether a cavity can dry safely without opening it.
Hidden growth and structural conditions
Soft, crumbling or distorted board, persistent odor and visible mold are reasons to reconsider drying in place. Painting or caulking a damp surface does not fix the source. In an older property, disturbing walls can raise other material-safety questions, so ask about local requirements before demolition.
What to request in writing
A scope should state which wall sections will be removed, why, how adjacent rooms are protected and how completion is verified. If a vendor recommends full removal, ask what conditions make partial removal inadequate. If the board stays, ask for the drying criteria and final measurement record. Reconstruction and painting usually come after the moisture problem has been resolved.