moisture meter technique

[Port]

Hi, I'm new to the business, so please allow me to ask what may be a dumb question. When I am checking a bathroom floor, for example, with a moisture meter, is the best method to check an area away from the toilet, tub, shower first to establish a baseline reading, and then put the meter at the base of the toilet, on the floor around the tub, etc., or should I just check the possible trouble spots first? Thanks

[Brandon Whitmore]

I do not even break out the moisture meter unless I already have concerns in the area. I will then check the area of concern and move out from there to "pattern" the area to see whether or not I am getting a false reading.

I believe urine has metals in it and will set off a meter even when there is no moisture left in the urine stained area.

At least or me, the moisture meter is only for back up of concerns I already have (personal opinion only on this as I am sure others use them all the time).

[chicago]

Great minds think a like as I actually asked that very question on another board today.

I was wondering about pipe sweat affecting readings in walls.

Also was curious if most guys always take readings in the attic on rafters.

[kurt]

I always go right to the spots; around the toilet, the base of a wall in finished bsmt's., the carpet tack strip in finished bsmt's., etc. I use a Protimeter SM, and there is no "baseline"; it reads moisture, or it doesn't.

One thing; if you are using the non-invasive type, standing water doesn't set it off. I tested stuff when I initially got my device; I'd pour a bunch of water on the floor, put vinyl flooring over it, then use the meter. It wouldn't read anything. After a half hour, w/the water soaked into the substrate & "spread out", it read the moisture. Anyone else tried this, or had similar experience?

What's most important is understanding the anomalies. Metal will set these things off; what you think might be moisture under the tile might be a metal fastener, metal corner bead, expanded metal lath, etc. Since there can be metal just about anywhere, it takes a while to figure this out. It isn't hard, but there is a little art mixed in the science.

Anything that looks like a leak gets checked. I don't randomly check moisture in rafters or other structural members unless there's something really strange or obvious.

[chicago]

Good answer.

I do know some guys are looking for levels over 15% content in attics as a way to backup concerns over inadequate ventilation

but was not sure how common of a practice this was,or how accurate an indication.

[randynavarro]

There are some ceramic tiles and granite / stone floors that can peg the meter depending on their mineral content.

Don't know which ones, but I find them occasionally.

So, yes, I take a baseline reading as far as possible from the fixtures before checking the base of toilets, base of tub walls etc.

[Port]

Thanks, guys. I'm sure experience will help a lot. Too bad my kid is older and doesn't miss the toilet anymore, so I can't test the theory of urine containing metals. I always wanted to put up a sign for him and his friends that said "We aim to please, so we'd be pleased if you aimed"

signed, The Management

[chicago]

Test it after a party.

I am sure a few of the guests will make good participents in your goal of further education.

[Scottpat]

I had an EIFS inspection last week and my meters were acting really screwy. After testing several areas that would be just about impossible for moisture to get into, I went inside and removed a light switch cover place. To my surprise the entire home had a Mylar type reflective barrier wrap between the substrate and the studs. The Mylar played havoc with my moisture meters.

[chicago]

These problems occur more with non-evasive meters I assume.

[Scottpat]

Originally posted by chicago

These problems occur more with non-evasive meters I assume.

Yes and no. You can still have false positive readings with an invasive meter if it contacts any conductive material in the wall. It's most common with the non-invasive or pinless meters. I always double and triple check my moisture readings, many times with a second or in some cases a third meter. Yes, I have several moisture meters and they all have their own special use.