Todays home inspector tool of the day is the trusty Moisture Meter.
This one is available from MSC Direct
The State Standards of Practice does not require us to use one, and consequently many home inspectors do not, but I think it is essential. This tool has to be used correctly, and it’s easy to do. First you have to make sure the home owner or listing agent does not see you poking the fine pins through the paint and into the wall or object. To do the test you stick the prongs in the suspected area and look at the number. On my meter, sometimes around 15% relative humidity will reveal a slight moisture issue. If it is up to 20%, it is definitely wet. It is important to test the same material in other areas around it or even in another part of the structure and compare the numbers. If it is 10% in the drywall everywhere in the home and the water stain shows 10%, then it’s dry.
That doesn’t mean there is not an active leak though. Maybe it hasn’t rained for two weeks and the spot is dry. Maybe the AC is not running and not producing a drip from the condensate line. So you have to apply a little bit of science and logic to figure it out. This home in Atlanta had a water stain but it measured around 13% relative humidity. Pretty dry but it hasn’t rained in a few weeks so everything is dry. No good evidence of a leak on the roof or in the attic. This stain didn’t have any mold development so I can only assume it is an old stain or a very slow, intermittent leak.
This tool has saved many of our clients money by identifying leaks that would have been missed without testing. We often find water damage near showers that has been recently painted to cover the leak.