Nuclear Roof Moisture Survey

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An accurate alternative test method for locating moisture laden insulation in almost any type of roof system, including buildings with multiple layers of roofing.

While Infrared Roof Moisture Surveys are the most accurate and efficient means of scanning most roofs, certain membrane types, roof systems, and environmental conditions can limit the IR cameras from detecting heat in moisture laden insulation. For these more difficult situations, a Nuclear Roof Moisture Survey is the best method for detecting subsurface moisture.

Using safe and accurate Troxler 3216 Nuclear Moisture Gauges, numerical readings are taken at regular intervals over the roof surfaces that correspond with the amount of moisture below the devices. Core samples are then taken to determine which nuke reading represents the threshold between wet and dry insulation and all readings above this threshold are deemed moisture laden.

This is the preferred moisture analysis method for roofs with thicker membranes, stone ballasting, reflective coatings, or multi-layered recovery systems, as well as the only reliable method for moisture detection in cold weather conditions.

Nuclear Moisture Surveys include…

Rooftop moisture analysis
- Nuclear moisture survey using 10′ x 10′ grid
- Rooftop marking of grid points, wet areas, and core samples
Written report including
- Moisture survey operating principles and procedures
- Roof construction and moisture content of core samples
- Quantification of all moisture laden insulation
Color CAD drawing including
- Roof plan to scale of all roof areas by numerical designation
- Locations of all moisture laden areas and core samples
PDFs and two hard copies of report and drawing

What Roofs Can Be Scanned With This Method?

Can Be Scanned

All Single-Ply Membranes
Smooth & Gravel Surface Asphalt BUR
Modified Bitumen (SBS) Membranes
Liquid Membranes

Must Be Scanned

Ballasted EPDM roofs
3-4 Ply Modified Bitumen Membranes
Aluminized Coated Roofs
Multi-Layered Roof Systems
Roofs During Cold Weather

Can't Be Scanned

Silicone/Foam Roofs
Metal Roofs
“Green” Roofs
Roofs Without Insulation

Benefits of a Moisture Survey

Locate moisture laden insulation
Isolate leak source areas and identify potential defects
Determine if a roof is in need of targeted repair or full replacement
Accurately determine the scope of work prior to issuing bid documents
Eliminate unknowns to dramatically cut down on up-front costs
Eliminate costly extras and change-orders during roof projects

Identify existing dry insulation to be incorporated into a replacement system, reducing overall costs and material waste.
Check the integrity and workmanship of a new roof system or repair
Ensure a manufacturer’s warranty will be issued upon completion of a new roof system

More about Nuke Surveys…

Prior to the survey, a CAD drawing of the roofs is generated with a 10′ x 10′ grid superimposed over each roof area. Once in the field, the intersecting points of the grid are measured out and marked on the roof surface with marking paint. Nuclear moisture readings are taken at each point and at other points deemed necessary or suspicious until an array of numbers covering each roof area is obtained.

The nuclear gauges are actually detecting hydrogen by expelling neutrons down into the roof system. They pass through all materials except hydrogen, which bounce some of the neutrons back to the device for detection. Many common building materials contain hydrogen and do slightly affect the nuclear readings, but the devices respond most significantly to concentrations of moisture in all types of roof insulation and recovery boards.

Because of the various combinations of building materials that may be present in a roof system, each roof reads a little differently and the meters must be calibrated to each system through core sampling. Core sampling typically starts at a location with a nuclear reading close to the median value of all readings. If the insulation is dry, another core is taken at a higher reading. If it’s wet, another is taken at a lower reading. This process is repeated until the nuclear reading that represents the threshold between wet and dry insulation is determined. We use great consideration and our years of experience to take as few core samples as possible while still obtaining the necessary information, and all core samples are properly patched according to the membrane type.

Once the moisture threshold is determined, all nuclear readings above this threshold are considered moisture laden and are outlined on the roof with marking paint. This information is then used to generate the final CAD drawing and report which details the results of the moisture survey and quantifies all moisture laden areas.