It reads the roofs infrared cannot.
Through ballast, through cover boards, through overlay after overlay. In daylight, in any weather.
What it actually measures
A calibrated gauge reads hydrogen content through the roof assembly. In a roof, hydrogen in any quantity means water, so the reading maps to moisture held inside the insulation.
Readings are taken at marked points on a grid walked across the roof. Nothing is cut, nothing is opened, and the roof is left exactly as it was found. The grid becomes a map of where the assembly is wet and where it is sound.
It is deliberately a different physical principle from infrared, which reads surface temperature after sunset and infers what is underneath. Nuclear measures through the assembly directly, which is why the two find different things and why carrying both matters.
The roofs that need it
On a simple, dark, exposed roof with good sun on all of it, infrared is faster, cheaper, and covers 100% of the surface rather than sampling it. We will say so. These are the cases where it will not give you a trustworthy answer.
A roof that has been recovered two or three times is a stack of assemblies. Infrared reads the top of it. Nuclear measures moisture held in the insulation below added membrane.
Stone ballast and paver-surfaced roofs defeat a thermal scan completely. The overburden is what the camera sees.
Thick cover boards flatten the thermal signal until the difference between wet and dry is no longer readable.
The white, high-albedo membranes specified everywhere now are working against a thermal scan by design: they are built to shed solar gain, which is exactly the signal infrared needs. Reflective roofs are a common source of false negatives. Nuclear is indifferent to colour.
Adjacent buildings, tall equipment screens and rooftop plant leave parts of the roof without the solar loading infrared depends on. Nuclear reads the shaded bays exactly the same as the exposed ones.
Infrared needs a clear evening after a day of real solar gain, a decent day-to-night temperature swing, low wind and no rain in the previous 24 hours. Nuclear runs in daylight, in any season, on the day the crew is there.
Grid readings produce comparable values across the roof, which holds up better in a capital plan, an insurance file or a dispute than a thermal image does.
The limits, published
Every method has them. Most testing firms leave them for you to discover after the invoice.
It is comparative, not absolute. A survey tells you this part of the roof is significantly wetter than that part. It is not a moisture percentage you can quote to three decimal places.
It cannot tell active moisture from historical moisture. Water that got in five years ago through a breach since repaired reads the same as water coming in tonight. That is a question for electronic leak detection, which finds the breach itself.
Deck condition affects it. Voids, previous repairs and changes in the assembly across a roof all shift readings, which is why the survey is read against what is actually up there rather than in isolation.
It does not guarantee finding every wet area. Nothing does. A survey that claims otherwise is being sold to you rather than explained.
All of that goes in the report, alongside the observed conditions on the day. A report that states its own limitations is the one that survives being read by somebody else's engineer.
The gauge is licensed, and that is the barrier
A nuclear moisture gauge contains a sealed radioactive source. Owning and operating one means licensing, trained and named operators, transport rules, storage requirements and record-keeping. It is not equipment a firm picks up because a job came in.
That is the reason only about three of the eight competitors we surveyed carry nuclear at all, and it is the reason a roof that needs it often gets an infrared survey instead, from a firm that only owns a camera.
So here is ours, in full, because a claim you can check is worth more than a claim you cannot.
1050897 - RAD250001
New Jersey Department of Environmental Protection, Bureau of Environmental Radiation, Radioactive Materials Program
30 April 2034
Todd Marcus, named on the licence. Every operator works under his training and supervision, which is a licence condition rather than a company policy.
The licence covers use at temporary job sites, not just at our own premises. Without that a gauge cannot legally leave the building.
Troxler portable moisture density gauges, model 3440 and 3400 series. The industry standard for this work.
Currently working under temporary reciprocity while permanent Florida licensing is finalised with the state. The number will be published here when it issues.
Ask any testing agency quoting you nuclear work for their licence number and the issuing authority. It takes a sentence to answer if you hold one.
Why this matters more in Palm Beach, Broward and Miami-Dade
Florida commercial roofs get recovered and storm-repaired repeatedly, and each round adds a layer. What ends up on the building is a complex, multi-layer assembly with moisture trapped somewhere inside it that a thermal scan simply cannot read through.
That is the case nuclear was made for. It measures moisture within the insulation even beneath added membrane, which turns a roof nobody could properly assess into a roof with a defensible moisture map.
It matters commercially because of who needs that map: condominium associations, ownership boards and facility managers building a capital plan, and anyone assembling documentation an insurance carrier will accept. Accurate moisture mapping cuts unnecessary tear-off, and it stops saturated insulation being left in place under a brand new roof.
What you get
A roof plan with the grid, the readings and the wet areas delineated against the dry, plus the boundaries between them drawn so the work can be priced. The conditions on the day and the limitations of the survey stated in writing.
We are independent. We do not sell roofs, we do not do the repairs, and we carry infrared as well, so recommending nuclear costs us nothing if your roof does not need it.