Moisture Readings For Tile Enclosures

As part of my bathroom inspection routine, I scan tub/shower tile enclosures with a Protimeter Surveymaster, looking for moisture intrusion that may have entered through the grout, causing wet areas behind the tile. I know from experience that the readings seem to be accurate, as I discovered in my own home. When the tile was removed, the green board was wet in the areas that tested high moisture levels with the meter. During an inspection last week on a 4 year old home, very high levels were detected within the shower stall, predominately along the lower half of the walls. The pan was the typical fiberglass, so there would not be a liner placed up the walls. Cracked grout was evident, the probable source of any intrusion. The sellers were not happy, stating that the cement backer board would prevent any damage. This may be a valid point, but if the grout is properly sealed, the water should not migrate to any backer board. Looking for opinions and alternate methods of inspecting tiled surfaces.:slight_smile:

The owner was partially correct. The cementitious backer board itself will not be damaged. BUT… that does not mean the framing in back of the wall is not being affected by moisture. If moisture can penetrate 4-6 inches of concrete in a garage floor, what makes you think it can’t penetrate a 1/4" panel and get to the wood structural members? You won’t see the manufacturers of cementitious backer board claim that their product will inhibit water vapor, because it doesn’t.

Water vapor can also be a significant problem if a shower or tub wall is on an exterior wall, especially in colder climates. During cold weather, if a vapor barrier is not present on the warm side of a wall system, water vapor can pass through insulation and subsequently condense on the cold side of the wall. This condensation leads to serious water damage in short order.

Unless you go with the Mike Holmes, “I have to tear it all out to see what’s wrong” theory, you are going about it correctly.

I scan the tile walls (and floors, especially around toilets) all the time. Water penetration is water penetration, even with cement board.

I also recommend, always, that they seal the tile grout and use silicone clear caulk on all inside corners of the tile (where it cracks) and a preventative measure.

Have you ever seen cement board when it’s soaked over a period of time? It still goes to mush. Doug

I also scan bathroom floors, in fact there was moisture below the floor tile in front of the shower at this same property. Sealing grout and caulking is included in all of my reports.

I use the same meter has you do and it show wet on cement floor that his many years old, so i wonder if we have a accurate reading when tiles are set directly on cement floor

The moisture meter will detect the ground moisture coming up through the floor concrete.

Thank Doug
So if ceramic tile are install directly on the cement floor the reading show damp it doesn’t mean that we have a foundation leakage, His that correct ??


I always establish an “average” reading on the surface of the material I am scanning. Yes, you will typically show high readings on a concrete floor. In the case I initially described for this post, I scanned the upper areas of the shower surround and had average readings 10-14%. The lower portion of the walls progressed to above 90%. Same backing material, top & bottom.

As with all tools in our equipment bag we have to know their limitations. Interpretation of our readings comes based on experience. Ask the thermal imaging guys about this. Use the moisture meter as a guide & look for reasons/problems that cause that situation.


Becoming a daily ritual. My tile guy is getting a kick out of these no speaka da english kind because they are keeping him extremely busy.

Here are some of my recent ones, notice the weep drain at the top of the shower pan on pic#1.