AT THE SUGGESTION of Jon Cochrane, a general contractor who has dealt with water intrusion, I bought a well-regarded, dual-mode moisture meter (combined pinned and pinless type) for $57. I tried it out in December (one day after the synagogue received nearly 1" of rain) and again in January (right after more than 3" of rain in one week, followed shortly by another 2.5" in two days).
Executive Summary
The inside of the south wall gets measurably damp due to rainfall, especially its lower portion (the concrete stem wall). After a hard rain, nearly the entire eastern half of the south wall (measured at various heights within 6' of the floor) gets so damp that it consistently registers off the scale.
What is a moisture meter?
A moisture meter is an electrical instrument designed for use in water damage restoration and building construction. It measures the moisture content of wood, drywall, or cement board.
This particular device works in two modes. In Relative mode, it detects moisture up to 3/8 of an inch below the surface of drywall, a quarter of an inch below the surface of cement board, and 3/4 of an inch below the surface of wood.
The readings show relatively drier versus wetter areas for a given surface. (This mode is often deployed to locate a water leak beneath a surface.) The relative scale’s display is in the form of a bar graph, consisting of 9 LED lights. Going from left to right, the first 3 lights are green; the second three, yellow; and the last three, red.
In Absolute mode, the device employs two steel pins as probes to assess the moisture content on or near the surface of building materials.
Relative Moisture Testing
In December, the 3 lower openings cut into the wall did not show any damp spots on the top of the exposed sill plate. The bottom of the sill plate showed about twice as much moisture as the top, but still not setting off any alarms.
When checking the interior wall surface, I did find one markedly damp area of plaster wall a few feet to the east of the 1st opening, a few inches above and below the sill plate. (The surface there was also colder to the touch than the surrounding wall area.)
When I tested again in January, surprisingly the interior surface dampness was not localized but widespread. Nearly the entire eastern half of the south wall (measured at various heights within 6' of the floor) was so damp that it consistently registered off the scale — even the sections that outwardly looked normal. (In contrast, I spot-checked the interior walls for calibration; those readings all remained in the green zone.)
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| 3' from the floor, at Row 15 (As usual, click/tap on a photo to enlarge it.) |
The foundation (stem) wall was also damp to an off-the-scale degree. This is not normal!
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| Exposed concrete foundation wall, below the post |
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| Near the floor level, at the foundation wall, Row 2 |
Absolute Moisture Testing
Tested in January via the absolute mode, the foundation wall again registered high or off the scale (i.e., more than 33% moisture!).
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