Flat roof survey methods: Nuclear vs Infrared

Category: Infrared Technology

Flat roof are a low cost solution to cover buildings but are notorious defectuous. We have already talked about the 5 most commons flat roof defects. Water infiltration cost companies thousands of pounds every year in repairs to address structural damage, rot and mould, insulation breakdown and in increased heating bills to address cold and damp inside the building.


When it comes to flat roof leak detection, there are a few different flat roof survey methods to choose from. Whilst infrared is by far the most common, electronic leak detection and nuclear moisture survey are also commong.

Here we compare Nuclear Troxler flat roof survey method with infrared flat roof survey method. 

Flat roof survey: Troxler Nuclear method

Oradio activity warning symbolne of the main concerns that some may have about this method is the word ‘nuclear.’ Whilst Troxler nuclear survey devices are built and tested to the highest standards, any surveying company using one will also need proper licensing and clearance for their use. Sstrict Health and Safety protocols apply but despite that, the word ‘nuclear’ is still likely to present a problem for many.

With infrared a viable alternative, few will opt for a nuclear survey. Aside from the difference in technology, a Troxler Nuclear survey also differs in its methodology.

In a nuclear survey, the technician must first draw a grid pattern on the surface of the roof in its entirety, usually with chalk or spray paint. The technician then takes a reading with the Troxler gauge at every point on the grid and marks the readings on a hand-held or computerised plan of the roof.

When the technician has full readings, they take core samples from areas showing the highest moisture content. If moisture is present, they take further samples of lower moisture areas, until they find dry roofing.

At the final point, the technician compares a bar graph that translates the readings of the Troxler nuclear survey and combines those with the core readings. This gives a picture of how much of the roof has moisture infiltration and to what density.

  • Despite being safe and regulated, the nuclear element is always going to give pause for thought.
  • A Troxler nuclear survey works grid by grid across the entire roof area, making it a thorough method.
  • Such a method combines core samples and graph data to build a picture of moisture infiltration.

3 issues with Troxler nuclear flat roof survey method

  1. Administration and transportation associated with the nuclear material contents.
  2. Long surveying time. A 50,000-foot roof area can take several days to survey.
  3. Poor sensitivity to moisture levels.  Roof consulting and engineering company  Crenshaw  Consulting Group  noted that the nuclear survey did not indicate high moisture levels in areas with trace amount. Because moisture can swell and shrink over the course of a day, this could mean missing areas.

Flat roof survey: Infrared method

infrared camera and operatorPerforming a flat roof survey with an infrared camera can help reveal troubling anomalies relatively quickly, showing clearly where moisture is trapped in a flat roof system.

The thermographer will usually perform the survey after the sun has set. This allows the surface of the roof and surrounding air to return to neutral temperatures and enables readings that are more accurate. During the day, a roof can retain heat, which makes it much more difficult to gain true, accurate readings in an infrared survey.

Damp and moisture infiltration often makes its way into insulation. During the day, this moisture heats up. When the sun goes down and surrounding insulation cools, the trapped moisture retains its heat. This makes it much easier to see with an infrared camera.

The thermographer can then spot these trouble areas. This will allow the roofing contractor or building surveyor to mark them out and investigate by taking samples from any suspect areas to corroborate  with the infrared results. Once confirmed, the surveyor can mark problem areas on a plan of the roof and the building owner can take appropriate action.

  • An infrared survey is performed after sundown to eliminate heat reading that can accumulate over the day.
  • Moisture leaks often bleed into insulation. Insulation with damp problems retains heat for longer than dry insulation, making it visible to infrared readings.
  • The building surveyor then marks problem areas on the roof, takes samples and is likely to confirm infrared readings.

According to a research paper by Crenshaw Consulting Group, infrared technology offers the best way to gain a good overview of roof substrate moisture conditions. The paper also notes that infrared technology is adept at identifying multiple, very small areas of damp.

3 Advantages of infrared flat roof survey method

  1. Easy to move around and operate. One man with a camera or if required a drone.
  2. Short surveying time: in a few hours, an infrared camera can survey 100,000+ feet of roof space.
  3. Clear and immediate results which may be confirmed with physical sampling.


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