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What to do about a damp bathroom wall?

johnnyd

Hey guys, finally got a moisture meter to check on the bathroom walls, is this normal?

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EricL

Hello @johnnyd

The manual for your new moisture meter should help you interpret the readings correctly. Different moisture meters have different scales depending on the material being tested such as wood, concrete, drywall, and tiles.

The manual will usually include:

Material-specific moisture ranges (e.g., what percentage is considered dry, moderate, or wet for different materials).
Calibration instructions to ensure accurate readings.
Mode settings (some meters have separate modes for wood, masonry, or drywall).

Since you're testing a tiled bathroom wall, check if your meter has a masonry or tile mode. If it's not designed for dense materials like ceramic tiles, the reading might not be accurate, and testing grout lines or exposed wall sections may give a better indication.

If you need further assistance, please let us know.

Eric

johnnyd

Thanks Eric! Changed to Masonry mode it doesn’t look good…

EricL

Hello @johnnyd

The higher number does not fill me with confidence. You'll need to look at the chart your manual has provided for you in order to determine how much moisture is being held behind the wall.

If your digital moisture meter is reading 32.2% on a tiled bathroom wall, it could indicate excess moisture behind or within the tiles, grout, or substrate. But please consult your chart just to be sure.

This could be caused by:

Leaks behind the tiles – If the waterproofing behind the tiles has failed, water can seep into the wall, leading to high moisture readings.
Grout or silicone failure – Cracked or missing grout and deteriorated silicone around joints (especially near showers and bathtubs) allow water to penetrate.
Condensation buildup – Poor ventilation can lead to long-term moisture retention, especially if the bathroom lacks an exhaust fan or windows.
Rising damp or plumbing issues – If the affected wall is shared with another room, moisture could be coming from a leaking pipe, vanity, or nearby structure.

What to Do Next:

Check for any cracks or missing grout and regrout if necessary.
Inspect silicone seals around the shower, bath, and sink—replace if peeling or mouldy.
If possible, take a reading on the opposite side of the wall (e.g., in an adjacent room) to see if moisture is spreading.
Improve ventilation by using an exhaust fan or opening a window after showers.
If moisture stays high, there could be a waterproofing failure or a hidden leak, which may require further investigation by a plumber.

If you're planning to paint, retile, or renovate, you’ll need to fully dry out the wall first to prevent further damage.

If you need further assistance, please let us know.

Eric

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