Moisture levels in basement


I posted this under the Infrared section as well because I did not know where it fits best.

Hello all,

My home inspector used a moisture detector on a tile basement floor of a house built in the 1920s. The house is structurally sound with very few problems.

The inspector found moisture in some very specific/small areas of the basement tile floor. Tiles nearby gave either very low or no moisture levels. The infrared camera reading was inconclusive in this area. There was a water leak in the home in 2011 that was repaired and all walls in the basement tested dry. There is a small crack/heave in the tiles in this area, but the owners insist that this crack has been here for a long time. There is currently a hole in the roof flashing that is allowing low moisture levels in an upstairs room.

My question is: How likely is it that the moisture detector was sensing some sort of reflection off of the tiles given that the infrared camera could not detect moisture? In that the moisture levels were found in such a small area, how likely is it that this could cause major problems in the future? Last, is it possible that a roof leak is causing problems in the basement floor only (and not the walls)?

Thanks so much for any advice on this topic!

To start with a moisture meter is designed and calibrated to detect moisture with respect to wood. Other materials require calculations based upon their substance. This information is not readily available to your home inspector. A very low moisture reading in one material could actually be a very high reading based upon its material.

There are several types of moisture meters and some can measure moisture in tile and some cannot.

Second; an infrared thermal imaging camera is “not” a moisture meter.
If anything is going to see “some sort of reflection” it’s going to be the infrared thermal imaging camera.

The thermal imaging camera can only detect conditions associated with moisture if an appropriate procedure was conducted during the test and the user has the ability to analyze the test results properly.

What does the inspector know about either one of these test procedures?

You can use a moisture meter and compare the readings from one material in one area to the same material in another. Certain materials will hold a certain amount of moisture. How much humidity is in the air is a very important factor to consider, affecting the more porous materials first. A highly experience home inspector can be successful using a moisture meter to find leakage. It is no way fool proof, but I do it all the time with great success.

so I guess the next question is , what is the hygroscopic capacity of floor tile?

Or more simply put, how wet is too wet…

You use the moisture meter in different places of the same tile floor to get a baseline reading. You’re not out to give specific, accurate moisture levels readings, just to determine whether some parts of the floor had significantly higher moisture level readings than others, which might indicate that more investigation was warranted.
If you get elevated readings, mention that in the report and let the client decide if they want to pursue it further.