I know that there are electronic methods for detecting leaks in membranes used to protect roofs. Basically they sense anomalies or interruptions in electrical conductivity. These interruptions are typically in the form of cracks or tears. I have not yet heard about any similar device being used to detect damage to clay tiles with results that provide any useful information. I would certainly question the validity of any claims made by anyone using a device for which they cannot provide proof of effectiveness validated by an unbiased testing and certification organization.
Fractures, and variations in density are very different things. Hail impact does not produce changes in density in clay tile to any degree that affects it’s ability to shed water, which is the most important criteria in evaluating clay roof tile.
Proper vitrification and solid continuity are key to the ability of tile to shed water. Levels of vitrification are not changed by impact from hail, however continuity can be interrupted by cracks.
According to the amount of impact energy carried by a hailstone, impact may create a crack that:
- propagates a short distance and does not continue through from the face to the back of the tile.
- propogates clear through the tile but is limited in length and width so that it does not allow through-tile leakage, but may trap and hold water that may, over time and in an environment subject to freezing weather, expand relatively rapidly (1-5 years) to finally allow moisture intrusion of the tile.
- splits the tile into two sections.
I question what useful information removing a tile from a roof and testing it for microscopic cracks provides.
- The drying process during manufacture of clay tiles creates micro-cracks of various sizes that may easily resemble micro-cracks created by the impact of hailstones carrying low impact energy and that carry a very similar chance of long term problems. Thus, micro-cracks from hailstone impact are not really a concern.
- Relatively low quality clay tiles can have visible shrinkage cracks and poor vitrification that may give the same results as hail induced cracks with limited propagation.
- If a tile is split, an electronic device is not necessary to determine the extent of the problem.
So, you’ve got someone taking one, or a few tiles off the roof to test them to show… what exactly? And what does showing the condition of a few specific tiles prove about the rest of the roof?
I’d say he refused to tell you because the information produced by his “instrument” meant nothing.