From Whence It Came

A simple fact about construction is that we do not use any material that will last indefinitely. If you don’t maintain your building it will fail, piece by piece.

That picture shows a terra-cotta block partition in an abandoned building. It was probably painted when first constructed and repainted at least once; the paint is failing in large part because the terra cotta surface is failing. If terra cotta is wet long enough, it gradually starts turning back into clay. In this case, it looks like the paint doesn’t breathe and is therefore trapping water inside the blocks. When the building was abandoned – and water started getting in, and condensation wasn’t driven out by heating, and freeze-thaw cycles started happening inside – then water was trapped behind the paint with nowhere much to go.

This damage isn’t particularly dangerous. I wouldn’t want to be near that partition when it collapses, but it’ll give a lot of warning before it does so. It’s a good indicator of conditions: if the base structure of the building, which in this case is reinforced concrete, is in the same condition, then there are real problems. The concrete is more resistant to damage than the terra cotta, so the indicator is more likely to give false positives than false negatives, which is also good. That makes the terra cotta a conservative indicator, which will show damage in conditions where the concrete might be damaged (and sometimes when the concrete is not damaged) and won’t show damage when the concrete isn’t damaged.