By John P. Monroe, RA
Level III Thermographer, Certification # 49004
Infrared thermography is becoming an increasingly common diagnostic tool for engineers, architects, and building investigators. Used effectively, it can help locate defects in the design and construction of buildings and building systems, saving clients time and money. Below is an example of how I used infrared thermography to help solve a water infiltration problem.
One of my frequent assignments at RAND Engineering & Architecture, PC is conducting leakage evaluations. I was recently assigned a leakage investigation at a college dormitory building in New York City. The building is 15 stories high with a centrally located three-car elevator system. The elevator bulkhead on top of the main roof houses electrical equipment in the front section and mechanical equipment and the elevator cars in the back.
Each dormitory suite has a kitchen and bathroom, and the bathrooms adjoin the rear wall of the elevator shaft, as depicted in the plan to the right.
Leaks along the elevator shaft during a heavy rain storm had damaged the electrical equipment on top of the west bank elevator and had infiltrated the 15th floor hallway ceiling along the north side of the elevator shaft. The other leaks occurred along the 12th floor bathroom ceiling, the ceilings and walls of the 11th floor dormitory room bathroom, and the 10th floor dormitory room.
I reviewed the leaks with the client and surveyed the roof assuming that’s where the water infiltration originated. I saw severe blistering of the roofing membrane along the west side of the elevator shaft. When I stepped on the blistered area, it was clear that there was a significant amount of water underneath the membrane.
There was also extensive plant growth on the roof. (Although another building on campus has a green roof, the plants I saw here were growing out of dirt and sediment that had collected from a lack of maintenance. There was also as an area of ponding and failed pitch pockets along the north side of the bulkhead.
These defects convinced me that the source of the leaks was the defective roofing system. After my visual survey, I used my Flir T-300 thermal infrared camera inside the bulkhead at the north section, where water was still present, and was able to determine that water was seeping through the elevator bulkhead walls where the roof was blistered along the west side of the elevator shaft.
My findings showed the roof defects to be the most likely cause of the leaks along the 15th floor corridor ceiling and elevator shaft. I assumed that water infiltrating at the roof defects was running down the riser pipe penetrations from floor slab to floor slab, which would explain the dormitory room leaks.
The riser pipes, however, are situated beneath the south side of the shaft, where I did not see any roof defects. The dormitory room leaks were occurring at the south side of the elevator shaft adjacent to the bathrooms. They reportedly started at the 12th floor bathroom ceiling and continued down to the 10th floor bathroom, where there was the most water damage. The 14th and 15th floor dormitory rooms appeared unaffected.
I requested access to the interior of the elevator shaft to look for signs of water infiltration into the shaft way. As viewed through the elevator shaft door along the west bank elevator, three of the enclosure walls are constructed of CMU block in-fill from floor slab to floor slab, with the elevator door openings located along the north wall. The fourth (south) wall consists of continuous metal framing covered with wallboard on each side. The dormitory rooms at each floor are “L” shaped and wrap around the rear of the elevator shaft.
As noted above, the bathrooms are adjacent to the elevator shaft. I didn’t see any evidence of water infiltration, so I took several infrared images of the south shaft wall. The infrared images show water infiltration starting at the bottom of the 14th floor slab and continuing down to the 10th floor.
I gained access to the interior of the 14th floor and 15th floor dormitory rooms along the south side of the elevator shaft to determine if moisture was present. The infrared images and hand-held moisture meter did not register any signs of moisture along the side of the wall, which was consistent with the images obtained within the elevator shaft. My infrared survey of the 13th floor dormitory room bathroom indicated moisture, and I confirmed this result using a hand-held moisture meter.
Based on my observations, the leak appeared to start at the 13th floor ceiling/14th floor slab and continue down to the 12th, 11th, and 10th floors. To continue my investigation, I requested probes be opened within the 14th, 13th, and 12th floor metal stud wall to determine if the source of the leak was a riser pipe within this bathroom wall. I recommended starting at the 14th floor bathroom wall because the infrared images led me to assume the leak started in the 14th floor wall cavity.
The 14th floor probe was performed above the toilet and exposed wet insulation along the main 4-inch cast iron riser pipe. Using a rigid borescope, I determined that the cast iron hub at the ceiling was cracked. Apparently, the heavy drain line volume during the rain storm caused water to overflow because the pipe could not handle the volume.
The infrared imagery enabled me to pinpoint the source of the leak more quickly than would have been possible through a purely a visual survey. In addition, I was able to locate the source with only one investigative probe instead of several, saving our client both time and money.
Infrared technology is not a substitute for a visual examination. Infrared technology detects infrared radiation (energy) from an object’s surface, but those differences in radiation and the patterns (infrared signatures) that they leave often indicate what is going on inside the structure.
There are common techniques for surveying a property’s conditions using infrared technology, but the most effective methods vary widely depending on the application, the building, and the defect detected. Thermography images should be carefully examined to determine the shape, patterns, and intensity of the colors. Each type represents the differences in radiation and emissivity (opposite of reflectivity) of objects in the image.
As a general rule, objects in the image that are lighter in color are warmer, and darker objects are cooler. The cooler spots, indicated by the purple/violet colors, must then be visually inspected to confirm they are water related. Moisture meter readings and investigative probes may also be necessary. Some locations that appear as cooler in infrared photos may not be caused by water but instead by drafts and missing insulation. But even in those cases, the infrared imagery points out heat and/or energy losses that may need to be addressed.
Ed: John earns 12 ITC certification renewal credits for this story. If you are interested in being published and earning certification renewal credits, send your story to firstname.lastname@example.org .