Answer
You can sometimes install drywall over an existing surface, but covering damaged drywall is not automatically an appropriate repair. An overlay may be considered when the existing assembly is dry, stable, securely attached, and suitable to remain in place.
Drywall should not be used to conceal active moisture, soft or sagging board, contamination, loose material, unsupported areas, electrical concerns, or damage that needs inspection. Adding another layer also changes wall thickness and can affect outlets, switches, trim, doors, windows, cabinets, and transitions. In many localized repairs, removing unsound material and rebuilding the affected section provides a clearer result than covering the entire surface. Moisture sources must be corrected and affected materials appropriately dried first. Westpeak can evaluate whether repair, replacement, or broader interior reconstruction is suitable.