Record when the leak appears
Note whether the stain follows rain, cleaning, tank use or air-conditioning operation. Include the affected room and time between water exposure and the visible symptom. A damp ceiling may receive water from a route that is not directly above it. Keep the observations factual rather than labelling the cause before inspection.
Inspect outlets and transitions safely
Accessible outlets, gutters, parapet junctions, pipe penetrations and equipment supports deserve attention. Check whether drainage is obstructed without entering an unsafe roof area. Previous patches can obscure the original detail. Explain where they are and provide any earlier repair record. A new patch should have a defined boundary based on findings.
Separate plumbing from rainwater paths
Water from a supply line, waste connection or service fitting requires the relevant plumbing assessment. Coating the roof will not repair a pipe fault. Conversely, replacing a fitting will not resolve a discontinuous membrane elsewhere. The investigation may involve more than one trade and should state what remains uncertain.
Agree the investigation before the repair
Ask how the accessible evidence supports the proposed scope, whether opening finishes is necessary and who reinstates them. Do not deliberately flood an uncertain roof to reproduce the leak. Follow an agreed test method. Read the detailed diagnosis guide and roof waterproofing information.