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Results: The laboratory analysis showed an unusual amount of silicon. Based on this result they concluded the streaks where caused by silicone bleeding from the grout joints.

I did a field investigation and discovered the following:

1. The silicone grout joints were in place for five years.
2. The streaking developed after four years; in other words, the streaking problem was about 1 year old.
3. The wall was cleaned daily with an alkaline cleaner containing sodium hydroxide(a soluble salt).
4. The company performing the cleaning had been hired about one month prior to the streaking problem.

The True Results

Based on the information I gathered, it was clear that the streaking was caused by alkaline cleaner and not the silicone caulking. If this was the case, then why did the laboratory results show silicone? The answer was simple. When the wall was completed, a silicone-based sealer was applied. The silicone sealer was detected, not bleed from the caulking.

This was a classic case where laboratory results led to the wrong conclusion. A good investigator will use both field and laboratory data to form a conclusion.

Putting It All Together

Once the inspection, investigation and interviews are complete and you have the lab test, then you can you render an opinion ... maybe! You still may have no idea what caused the failure. Then you can only state possiblities. I was once asked to render an opinion on why an installation failed, but the floor had been replaced, and all evidence was destroyed. All I could do was provide possible reasons.

If you do know what caused the failure, then you are ready to write and submit your report.

About the author:
Frederick M. Hueston runs the National Training Center for Stone & Masonry Trades, Asheville, NC 28806, www.ntc-stone.com, and can be reached at Fhueston@aol.com.