Thermal Imaging of Roofs

With all the rains we have been having across the country, roof leaks are not hard to find.
But how should a roof really be repaired. To you simply run to the local hardware store and buy some roof patch? Do you call a roofer and pay them to go on the roof and apply a bucket of mucket? What should a real repair entail? I am a Licensed AZ Residential and commercial Contractor as well as an AZ Home Inspector and I would like to address this question.

To answer this question we need to look at what issues are caused by roof leaks.

1. It leaks. Duh, there is water dripping from the ceiling creating a slippery surface below. So a repair must stop the moisture from getting in. But is that all?

2. Insulation looses its R-Value when it is wet. That’s right, if the roof leak soaked the insulation before it made it to the ceiling to drip on the heads of unsuspecting people, the insulation might as well not be there at all, in fact, no insulation would be better than wet insulation.

3. Wet insulation deteriorates materials it is in contact with. If your roof is wood or metal,the wet insulation will cause decay and or rust, effectively reducing the life of the entire roof.

4. Moisture trapped under the roofing can and will turn to moisture vapor and find a way back out of the roof, often causing additional areas for moisture to enter at a later date.

So what should a roof repair entail? In my opinion the repair should include removal and replacement of wet insulation and any damaged building materials.

To often, the entry point of the moisture is not even located. Someone makes a guess where the moisture is coming in and spreads some stuff on the roof, collects a check and leaves.
Wow, no leaks, (until it rains again)

Thermal imaging can be performed on many roofs to locate areas of moisture under the roofing. The wet areas change temperature at a different speed than the dry areas making it possible to locate problem areas and mark them for repair.
Here are a few examples:

Roof Inspection with infrared

Infrared Roof Inspection

The the top photo is what a roofer or inspector sees simply looking at the roof. Notice that there are several patches visible, but was the roof actually repaired?

The next image is what the thermal imaging camera sees using infrared technology. The red and yellow areas indicate a difference in the temperature, This area is then scanned with a moisture meter to determine if this a moisture issue.
Moisture is trapped under the surface and is holding the heat, thereby making it visible to the thermal imaging camera.

Here is another example:

What the eue sees

Wet area under roof shown with Infrared camera

The top photo shows that someone has tried to patch this area of the roof before.
The image on the bottom shows the temperature difference caused by the moisture trapped under the roofing. This moisture can turn to vapor when heated by the sun in the summer or your furnace in the winter. The vapor will dry to rise up and can cause blisters on the rood surface as well as weaken or even separate seams of the roofing materiel.

The moisture trapped under the roofing will also damage the building materials it is in contact with.

Think of this the insulation is like a sponge, it absorbs moisture until it can not hold any more, then the moisture drips down. If you had a leak under your sink would you dry out the area under the sink? I would hope so. As an inspector I have seen lots of shelves under sinks that are damaged or have been replaced due to leaks.

I have also seen lots of roof sheathing that has been damaged from roof leaks that someone simply patched. If there is no insulation against the roof deck then most of the time the deck can dry. If the insulation is against the roof deck and gets soaked, damage can and will occur.

If your building has a flat roof that is fairly new, I suggest finding someone experienced to perform a thermal roof scan. If the roof is older and has a history of leaks, I strongly suggest having the roof scanned and making the needed repairs now before more damage occurs from the moisture trapped under the roofing material.

If your in AZ, contact us to perform your roof scan. If your in a different part of the country, you can still contact us and we may be able to assist you in finding someone in your area.

We can be reached at or 480-636-7400
Scott is an AZ Home inspector with years of experience in the Arizona Home Inspections industry. He has taught Phoenix Home Inspectors, Gilbert home inspectors and professional home inspectors across the country.

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  1. This information is worth everyone’s attention. How can I find out more?

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