Communal Flats - Leak Detection

This top (7th) floor (base 1) flat located below the flat roof was affected approximately 3 weeks prior to our visit during heavy rainfall. The affected area is a small circular damp stain on the living room ceiling. Moisture testing of the affected area showed no raised levels of moisture indicating the issue is not ongoing. Salts testing proved negative for both chlorides and nitrates which further indicated rainwater as the cause. The water meter located in the meter cupboard in the hallway was static whilst all internal services were off indicating no internal leaks on the pressurised pipework. We tested all waste pipework in the bathroom and En suite using coloured dye and subsequently carried out endoscope inspections of the waste pipework in the wall voids behind and could see no moisture present. There are no internal pipe leaks in this property.