Measuring moisture under tile is crucial for identifying leaks, preventing mold growth, and ensuring proper subfloor conditions. While various methods exist, the approach often depends on whether you can access the subfloor directly or need non-destructive techniques.
One common method, particularly when access is possible, involves using moisture meters that measure electrical resistance.
Using Pin-Type Moisture Meters
A key principle in measuring moisture in building materials, including those under tile, is using tools like pin-type moisture meters. These meters are designed to assess the moisture content by leveraging the conductive nature of water.
How Pin-Type Meters Work
A pin-type meter's probes determine moisture content by measuring electrical resistance between the probes (pins). Since water is dampness-conductive, less resistance indicates a higher moisture content percentage. The meter sends a small electrical current between its pins. Dry materials offer high resistance to this current, while moist materials offer lower resistance because water contains dissolved salts and minerals that conduct electricity. The meter then converts this resistance reading into a percentage of moisture content based on calibration charts for specific materials.
Application Under Tile
To use a pin-type meter to measure moisture under tile, you typically need to access the subfloor or backer board beneath the tile. This often means:
- Removing one or more tiles to expose the underlying material.
- Drilling small, discreet holes through grout lines or the tile itself (though this is less common and can damage the tile).
- Measuring moisture in removed sections of subfloor or backer board suspected of being wet.
Once the underlying material is accessible, the probes of the pin-type meter are inserted into it. The meter then provides a reading indicating the moisture level.
Advantages & Considerations
- Direct Measurement: Pin-type meters provide a direct measurement of moisture content at the specific point where the pins are inserted.
- Accuracy: When calibrated correctly for the material being tested (e.g., wood subfloor, cement backer board), they can be quite accurate.
- Invasiveness: The primary drawback when measuring under tile is the need to penetrate the material, which means tiles often need to be removed or damaged.
While pin-type meters rely on electrical resistance and are effective when direct contact with the underlayment is made, other non-penetrating methods (like those using radio frequencies) are sometimes used to detect potential moisture areas under intact tile, although they typically provide relative readings rather than direct moisture percentages of the subfloor.
