VERTICAL CRACKING in the stucco of our pilasters might be merely a rupture in the stucco itself—without having compromised the tar paper (vapor barrier) behind the stucco. On the other hand, as a structural engineer told me today, it could be the opening for a serious structural issue to have developed: dry rot in the post, due to persistent moisture intrusion.
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| (As usual, click/tap on an image, to enlarge it.) |
It’s like when a car’s owner finds that one of its tires looks almost flat. Can that tire be patched—or does it need to be replaced? Well, it needs further inspection. Similarly in our case, the best way to find out what we are dealing with is: chip open a couple of the cracks, to see how deep they go.
Below the jump, this post looks more closely at the newly noticed cracks, and our options.…
Executive Summary
The 5 pilasters that are most exposed to the sun are showing long and deep vertical cracks. A structural engineer says that it would be normal and prudent to look more closely. What matters is whether the tar paper underneath has been compromised—and if so, how damaged the wooden posts might be.
Chances are good that the posts are fine. But we need to know what the actual condition is before deciding what ought to be done about it.
That’s why the contractor is assigning one of his stucco workers to come by and open up a couple of cracks, within the next week or so. It’s part of the prep for the pending waterproofing job.
What we can see from below
Last week, our waterproofing contractor came by for his first site visit since August. He’s gearing up to fix our exterior south wall this summer. Yet he immediately noticed long, deep vertical cracks near the corners of five pilasters. (Our previous structural engineering team did not remark on them, perhaps because I was focusing their attention on the ugly-looking pilaster bases.) Here are photos for 3 of the 5.
What it means
The contractor was concerned that the cracking could be a sign of trouble in the wooden posts, which support the roof. He was reluctant to simply fill in such cracks, without knowing whether they signaled a deeper problem: dry rot.
Today I asked a structural engineer about it, and he agreed that it would be normal and prudent to look more closely. Whether these cracks are actually a problem, he explained, depends upon how the metal frame behind the stucco was constructed. Repeated expansion-and-contraction (due to sun and moisture) often stresses a corner enough to induce cracking. That’s no surprise. (It’s the first place that stucco tends to fail in an earthquake.)
What matters, though, is whether the tar paper underneath has been compromised—and if so, how damaged the wooden posts might be.
Chances are good that the posts are fine. But we can’t rely upon mere probabilities when both structural integrity and waterproofing are at issue. (And when a wall is as weatherbeaten as ours has been, and has been as poorly maintained.) We need to know what we’re dealing with before deciding what ought to be done about it.
That’s why the contractor is assigning one of his stucco workers to come by and open up a couple of cracks, within the next week or so. Fortunately, June is the right time of year to do such investigating—after the rainy season.
A cosmetic crack
Here’s a photo of a less worrisome kind of crack: it starts at the pilaster and runs up to parapet wall.
The structural engineer explained that the wall above the pilaster does not bear any weight (other than its own). However, stucco is a brittle material, so when there is cracking in the pilaster, it’s not surprising that the crack might propagate upward.
Once the pilaster cracking below has been addressed, the rupture above it can be simply patched.
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