There are three vertically oriented cracks on the interior south wall of our historic sanctuary. Each of them has distinctive characteristics, so they may well be from different causes.
Our painting contractor has offered to patch and cover over these cracks, which he considers to be relatively trivial work. That is likely to be done this month. [Yes, done on 11/22. —DS] We both expect that the cracks will recur. Yet without a better understanding of their cause, periodic patching seems to be the best we can do.
Below the jump, this post documents the nature of the cracks.
Unfortunately, these cracks are difficult to document with photos, both because of poor lighting conditions in the sanctuary (with glare from sunlight through the windows) and because their length is so disproportionate to their width.
Crack at Row 4
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| (As usual, click/tap on an image to enlarge it.) |
This crack is the most subtle. It has a horizontal aspect that vaguely resembles a previous crack in this area (likewise coming down to the seats at Row 4; see this post), prior to the work last summer. Below the white plaster “frieze” band, the crack is quite straight. That makes sense, because the lath board there was replaced last summer with larger drywall sheets.
Crack at Row 14
Remarkably, this crack did not exist prior to the work last summer; it showed up during the winter (see this post). And it is the most pronounced of the three present cracks, even though it was patched less than 6 months ago (!). Both the crack and the wall itself are strikingly uneven.
Crack at westernmost window
This crack is the longest by far. It starts on the ceiling and runs down above the peak of the window well. A continuing crack runs along the left side of the window well. Below the white plaster “frieze” band, it runs pretty straight down to the floor.
This one is not entirely new. Before last summer’s restoration work, there was a large crack on the ceiling in this area, and evidence of wall patching (see this post). I had thought that was due to a roof leak, but now I’m not so sure.
What is going on?
I can think of a few possible explanations.…
Settling from recent construction? At Row 4, this explanation seems likely, because that is precisely where the 10"x10" structural post was replaced last fall. In the process, most of the interior wall there was opened and then closed up again (see the end of this post).
Building settling? Perhaps, but along the entire 100-foot-long wall seems unlikely. And settling would tend to show a shift on one side of a crack relative to the other, which is not what I am seeing.
Earthquake? Perhaps, but I am not aware of any significant earth-shaking in Venice. Still, according to one website, “[so far] in 2024, Venice has experienced 483 earthquakes with a magnitude of 0.1 or higher on the Richter scale.” Maybe there is a cumulative effect. Our frame walls have not yet been seismically retrofitted for shear strength, so they would be sensitive to vibrations. Yet on the opposite wall I have not noticed any cracking.
Water intrusion? Perhaps; the unevenness at Row 14 suggests moisture in the wall. But this wall was thoroughly waterproofed last summer (not a 100% guarantee, but still…). More to the point, it hasn't rained since March 30! (Well, to be precise: 0.07" on Apr 6; 0.38" on Apr 15; 0.12" on May 5; and 0.01" on Oct 26. Hardly enough to penetrate and damage a wall.)
Thermal expansion? Perhaps. On sunny days, the south wall is exposed to a significant heat load, including reflected radiation from the parking lot. The wall itself is not insulated, which means that the interior plaster/drywall is probably dealing with an unusual degree of expansion and contraction. It is the kind of thing that causes cracks to form.
And why are all three cracks so different from each other??
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