Drills or X-Rays?

Recently, a major engineering firm stated in its newsletter that it offers its clients a more accurate prediction of costs because it uses “non-destructive testing and evaluation (NDTE).” Such an examination – utilizing high-tech metal and moisture detection equipment, surface penetrating radar, and materials analysis – allows the engineer to obtain necessary information without using an invasive drill.

“It’s a visual examination, often using sensors and x-rays,” says Eric Cowley, principal at Cowley Engineering, “so you’re not breaking something open in order to examine [the space].”

If NDTE doesn’t give enough information, Cowley adds, “I would do an invasive test.” Such destructive probes are more expensive because the area that’s broken open for examination must be repaired after the testing is done.

If your engineer carries more gadgetry than James Bond, does that mean you get a better and less expensive project? Possibly. But Gene Ferrara, president of JMA Consultants, an engineering firm, says buyer beware: NDTE is only as good as the people running it, and deductive ability is more important than the equipment a firm employs. “There are a lot of people who use these cameras who don't know what the hell they're doing,” he warns.

Probes, overseen by a savvy engineer, are still the best way, Ferrara asserts. “You're never going to know a hundred percent of the story until you expose a hundred percent of the area,” he says. “We have jobs where we open up walls, and all of a sudden, you have a hidden brick tie corrosion issue, as well as hidden latent defects, or deteriorated spandrel lintels that you cannot see.”

Cowley agrees. “Experience plays a big role in whether you need to go ahead and chop something open or not,” he says. “Imagine seeing a vertical crack going up a corner of a building. I don't need to open that up to know that we have corroded steel, (but) I would need to open it up to see how corroded it is. Or brick ties – nobody does an X-ray on something like that. To find ties, you have to open the wall and look inside the cavity.”

In the end, says Ferrara, every building is unique, so uncovering structural problems requires a case-by-case approach.

“An engineer is like a doctor with a patient,” he says. “You can't always assume the same things for every building. You need a good investigator and diagnostician.”

Sometimes that diagnostician can do the job with non-invasive radar, and sometimes he’ll need a good old-fashioned pneumatic drill. Your engineer will need three things to make the right decision: experience, experience, experience.