A Data Point

That crack monitor was installed in the 1980s, something like 35 years ago, so it’s safe to assume that the crack in the plaster is at least that old. The monitor was epoxied into place, and it’s still holding on strong – I tried to move it any hand and couldn’t. So…what does it mean?

First, it means that anything we do may be less temporary than we think. This is a beautiful interior space, and I doubt the people who put that crack monitor in place thought it would still be there in 2019.

Second, it means we know less than we think we know. The fact that the crack monitor is still at zero does not mean there has been no movement in those decades. It simply means that the position now is the same as it was when the monitor was put in place. It might have moved in a daily cycle, or a yearly cycle, or irregularly during the intervening period.

Third, we need to look at secondary evidence. The crack monitor looks very official, what with its grid and being measured in millimeters, but the plaster is its own crack monitor. If there has been cyclical movement, the amount can’t have been very much or the plaster would be far more damaged.

Finally, the only data that matters is data that you have. If someone had photographed the monitor, or otherwise recorded its position on a regular basis, we’d have a great set of data points that would answer the second item in my list. But no one did. So we have one data point, on the day I was on site. Any time someone suggests performing tests, my first question is “what will change in our actions based on the answers from the test?” If the answer is “nothing” then I recommend not performing the test. The next question needs to be “How are we going to record the data so that the test retains its meaning when we’re not around to interpret it?”