Nuclear Roof Moisture Inspections
A nuclear moisture gauge uses a non-destructive testing technology and is used on a low-slope commercial roofing to determine the extent of moisture intrusion into the insulation of the roof system. These gauges can be used on most types of roofs, but are more common on ballasted single-ply systems, which are difficult to inspect using infrared.
Nuclear roof moisture gauges detect moisture using neutron thermalization.
A grid is laid out on the roof using marking paint and readings are taken at each grid point using the gauge. Neutrons emitted by the gauge are thermalized (slowed) by hydrogen molecules immediately below the gauge at the location being measured. The slowed neutrons are detected and counted by the gauge which yields a reading relative to the hydrogen content of the measured location.
Readings are recorded on a diagram of the roof corresponding to the grid layout of the inspection.
Readings on dry material, when plotted and grouped as a histogram produce a bell shaped curve. The mean (average) reading and standard deviation are used to determine the highest number (reading) that indicates a dry condition. Readings above this number are likely due to higher moisture content of the measured material.
Core sampling is then used to verify the calculated dry and wet areas of the roof system and determine where in the system the elevated moisture exists.