moisture testing

[tony lamar]

I'm kinda new to the moisture meter technology so bear with me. I recently purchased a Delmhorst BD-10 pin type analog read out moisture meter. They say you can also test concrete with it. To test concrete they say to drive masonry nails and touch the electrodes to them. I've just poured 10 bags of slc and would like to check the moisture content before laying laminate over it. The slc says ready for floor covering in 24 hours. I checked some that was down for 48 hours and get readings of 15-16 percent. Are there corrections that need to be applied to those readings since it's not wood? Seems a little high to me. Would that be considered an acceptable reading to proceed? How about with a vapor barrier? Please help an inquisitive dummy trying to do the right thing.

[Tandy Reeves]

Tony, laminate dances to its own drummer. Check with the mfg. and see what their top numbers are. The readings of 15 to 16% sounds high. What is the highest reading on the meter? How long did you wait after driving the nails into the slc? When driving the nails into the slc, the friction heats them up and the heat would draw moisture to them. You should wait some time before testing after the nails are driven in, other wise you could be getting false readings.

[hookknife]

false positives, noooooo goood

[tony lamar]

Thanks for responding, Tandy. I consider your input most valuable.
I didn't use nails for the slc. I just used the probes because it's soft enough to penetrate. I just noticed they have a correction chart with my meter for different species of wood,so it would seem, if corrections were needed for woods of differing species, that to change to a totally different subtance (concrete) might likely involve corrections as well. I really only mentioned the nails to point out that they claim you can test concrete.

Also,
on my meter, 15% is borderline red. The meter reads up to 40%. So I wondered if adding 6 mil plastic plus the foam which also has a vapor barrier, would be acceptable. It's Quickstep laminate by the way. May have to talk to one of their techies, huh?

Mr. hookknife, could you elaborate?

[Tandy Reeves]

Tony go with either 8 or 10 mil vapor retarder. Six is a minimum, it punctures easy, tears easy and is just a get by. Overlap the edges 6 to 8 inches, and cove the plastic up at least the plank thickness and you now have a nice little plastic bowl to protect the laminate from moisture along with the cushion.

[Chuck]

The problem stems from you putting stock in the reading you are getting. Sticking a pin meter in floor patch makes no more sense than sticking it in laminate or styrofoam.

Was this poured over a wood floor?

[tony lamar]

One room is on concrete. The rest is on wood. The part I checked is on wood. I'm not really putting any stock in the reading. That is why I'm asking the questions. If this isn't an accurate method, why? How would one go about accurately checking the mc of slc?
Scan type meter? What would be the upper limits once an accurate test has been established?

[Tandy Reeves]

you ask a very good question. When I think about it, the slt is more like gype-crete, therefore, I would test it like gype-crete. That is do the clear plastic 24 X 24 square taped to the slt for 48 hours. If there is condensation on the plastic or the slt under the plastic is darker than that outside, it is too wet. The pin meter is intended for measuring m/c in wood. You always stick the pin in the direction of the vessels in order to get correct readings. I have never found pin meters to be much good on anything but wood.

[tony lamar]

Tandy,
I had kinda picked up on that from the guys on here (you included). I just wonder why they (Delmhorst) say you can use this meter to test concrete, wood, sheetrock, and insulation. I bought it for wood anyway, but when I read their little booklet, it struck me contradictory to everything I'd heard. As I said, I'm new to this and I am really seeking knowledge. Seems as if moisture testing can be tricky and the methods and accuracy are debated among the various practitioners. Seems to be tricky to pin anyone down to a definite conclusion particularly with regard to concrete. Confusin. Ain't it?

[Jon Scanlan]

This sounds the same issue I brought up under Self Levelling Compounds. Any type of subfloor/ filler/ concrete/ wood/ or anything. To me if any type of moisture reading says wet or in the red it means STOP

[Chuck]

Actually, Tandy, SLC is more like SLC. It is loaded with very aggressive drying agents. What this means is that it is likely to be the driest thing in the house in about 24 hours.

This entire deal seems a waste of time to me. If it turns the right color, it is dry. The stuff dries from the bottom up.

[Danny Ferguson]

This may be a stupid question. If you poured slc on a concrete floor, and came back the next day and put down a 10mil vapor retarder and laminate pad, creating a plastic bowl like Tandy suggested, would the slc mc even be a factor for installing laminate in this area?

[hookknife]

If SLC's are mixed correctly, they are not a source of moisture, this is not a hard concept yet no one seems to understand it?????????? (except maybe chuck)Heres the word for the day HYDRATION look it up
Concrete Technology | Concrete Design and Production | Portland Cement Association (PCA)

[Jerry Thomas]

Danny, I don't know what you used there but I mainly use Mapei Planipatch. I can always lay the next day, after it turns the light grey. I don't trust those 3in1 pads either. I put down a 6mil poly lapped up the walls abit. I have not had any problems with it tearing on me, but the thicker the better if you can find an 8 or 10 mil poly locally.

[tony lamar]

Originally Posted by Chuck Actually, Tandy, SLC is more like SLC. It is loaded with very aggressive drying agents. What this means is that it is likely to be the driest thing in the house in about 24 hours. This entire deal seems a waste of time to me. If it turns the right color, it is dry. The stuff dries from the bottom up.

Likely? The "right" color?
Am I to understand that verification is a waste of time? Or is it the asking and learning process that wastes your time? Please try to be patient with the mere mortals. We're not all born on Olympus, so some of us have to climb.