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Getting Down to Work on the Roof – Conducting your Inspection

Last week, I went into detail on tips to help you prepare for a roof inspection by conducting a pre-inspection during daylight hours. Now, I will explain necessary steps to take while inspecting a roof in the evening, and what you can expect to see if there are issues.

Before you begin, it is important to call security again and, as needed, the local law enforcement to reconfirm your presence on the roof. If you used an extension ladder to get on the roof, it is a good idea to either tie to ladder off so it doesn’t blow over or, in many situations, to pull the ladder up on the roof—not an easy task but vital to keep others from following you up! Mark all the hazards you noted in your pre-inspection using both hot packs and “light sticks” so that you can see them both thermally and visually.

As I said a couple weeks ago, with ideal conditions, most Built-Up Roofs (BURs) will reveal themselves about an hour after sunset. Bald single-ply roofs with low-absorbent insulation may happen even faster, and ballasted roofs may take longer. It is a waiting game! You can’t rush the roof, but you do need to be ready. I keep walking the roof until I begin to see changes.

As the roof cools, the areas of wet insulation will show up as being warmer than the dry areas. The exact shape will vary with the type of insulation and the conditions.

As the roof cools, you’ll begin to see the areas of moisture trapped in the insulation as being warmer. For absorbent insulations, the pattern will often be a series of intertwined rectangles—the actual insulation boards—called a “board-edge” pattern. For low-absorbent insulation, the patterns can vary widely and are often less discernable. When you locate a suspect area, confirm your findings with a moisture meter, preferably a non-destructive one.  Typically, at that point, your escort will mark the edges of the wet area with paint. I recommend you mark as close to the actual shape as is practical—again, on BURs you can often get within an inch of the actual wet/dry boundary. Number each area for reference and take any thermal and visual images needed to document your findings.

Move over the whole roof scanning about 20-30 feet out in front, but remember, it is dangerous to move while also looking at the thermal image. You’ll actually be somewhat “night blind” because of the bright screen, so it is far better to move to a location, guided by your flashlight, and then stop and look around using your imager. Again, the primary job of your escort should always be to watch out for your safety. When you are within 10-feet of the edge of the roof, you may want to take special precautions. Even a 6-inch change in elevation can be a big problem if you don’t see it coming, so always keep safety as your first priority.

While it is important to work as quickly as you safely are able to, don’t rush things. Getting in a rush always creates an unacceptable

Always work with an escort on the roof and follow good, safe work practices, especially near the edge.

safety risk. You’ll be tired as the night gets longer and longer. Take a break and enjoy the stars or catch the 9th inning of your favorite ball game. At some point you’ll either be finished or realize you’ll need to come back. With good conditions, experience and a roof that is not completely wet, I have often inspected up to 200 squares of roof in one night. If you need to inspect a larger or more complex roof, it’s best to just plan on two nights.

When your night’s work is done, pack up, notify security and enjoy getting some rest. The follow-up can vary depending on the customer’s needs, but often includes another trip up on the roof in the daytime with the owner and the roofer to verify your results. Remember, the fact that you located the areas of wet insulation is the key information needed to extend the life of the roof. If the roofer can remove that wet insulation and patch the membrane back, the owner ends up with a “like-new,” leak-free roof and everyone is much farther ahead than before you arrived on the scene. Nice work!

Whether you’ve been up on a roof or not, I would also recommend you take a look at our on-demand webinar, Low-slope Roof Moisture Inspections ($59). It is a great primer for those new to this application and an excellent refresher for those have some experience. You’ll learn a lot and see many images that we could not include in this blog post.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

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