About a year ago, my wife and I purchased a new construction home (in Northern Virginia) whose flooring turned out not to be flat. In order to fix the problem, all of the flooring had to be removed and about 1/3 of the subfloor (OSB). The new flooring was delivered a little over 4 weeks ago -- it's 3/4" solid hickory in 3", 4" and 5" widths (which will be installed in a 3-4-3-5 pattern). The problem is the moisture content. The difference between the old OSB (readings in the 9's and 10's) and the new flooring and OSB (readings in the 6's and 7's) has hardly changed. Over the 4 weeks the moisture content in the Hickory and new OSB has gotten higher, but so has that of the old OSB. The manufacturer's installation instructions state that the difference between the flooring and the subfloor should be no more than 2. Does anyone have any idea how long it might take for the difference to get in range? Is there anything that we could do to help the acclimation process? How nasty are the consequences if we have the flooring installed with the current difference? Any suggestions would be greatly appreciated.

Thanks,

Paul

p.s., If I can provide any additional information that would help, please let me know.

What instrument are your using? If you call the manufacturer of the instrument there is usally a conversion for solid to ply or OSB.

"Use your pin moisture meter to measure your wood flooring material. Take multiple
measurements and average the results. The NWFA recommends measuring the moisture
content of 40 boards for every 1000 square feet (Do not just measure the ends of the
boards that are on the top of the pile). The boards should be selected provide the most
accuracy survey of the moisture content. When using a pin meter it is important that you
push the pins in as close to their full length to ensure good, consistent contact with the
wood fibers. Using an insulated pin allows you to penetrate to whatever depth is
appropriate for that thickness of wood.
Use calibration charts supplied by you meter manufacture to adjust the readings for your
sub floor and hardwood finish. Some meters have built in species correction factor that
may be utilized.
The APA evaluated the equilibrium moisture content of structural panels. The results
indicated that the moisture content of plywood and OSB at a given relative humidity is
lower than the published values for solid wood. The APA data below is based on an
absorption cycle at a temperature of approximately 70°F. (APA Form No. TT-028A
December 2006)
Use the EMC chart below to calculate the appropriate moisture content of the sub floor
and wood finish and then check against the actual reading you have recorded.
The NWFA recommends maximum difference between the sub floor moisture content
and finished wood moisture content of 4% for strip flooring and 2% for plank flooring."

Sorry the chart will not copy.

Hi,

Thanks for the reply and the information.

The moisture reading is being taken by a person from the flooring subcontractor, and the meter is of the pin type. He's coming tomorrow to take another reading, I'll take a look at it then.

Also, it appears that this subcontractor just works with large builders. As such, they don't (normally) bother with moisture readings (as evidenced by the fact that I had to repeatedly bug them to even take measurements). The flooring gets delivered to the job site and it gets installed that day -- I was told that they do this to prevent it from disappearing. I mention this because I'm starting to believe that they don't know the proper procedure for taking moisture readings. For example, given the guidelines in the information that you provided, he should be sampling about 25 boards, not the 7 or 8 that he's using.

This leads to another question should the boards be out of the boxes that they came in? I did tear off the ends of the boxes, but that's it.

Thanks,

Paul

You dont want to just open the ends, they will dry or gain MC faster then the interior of the wood in the boxes.

Now you might as well open them and stack them criss cross. Solid hickory is a wild card.

Testing assumes the tester knows how to use the meter. What adjustments must be made for each species of hardwood. Whether the moisture readings taken are in line with the humidity levels in the home. Example a 5% moisture content reading would be attained if the ambient relative humidity readings in the home were at 25%. 7.7% moisture content readings would be attained if the ambient relative humidity readings were at 40% the ideal installation midpoint of the 6% to 9% wood is mfg at.
Subfloor may not be higher than 12% regardless. Readings for plywood, osb or solid wood subfloor are not the same and must be accounted for when taking subfloor readings.
Now if the person taking the readings does not understand any of the above find someone who does. Take photos of all readings and their location in the project to document time and date for this will be crucial later if there is a failure. Particularly if you need to go to court.
When rh levels are allowed higher than 75% look for the clause that states if there is ground cover under the slab. If there is not a 95% allowance will not be allowed by most adhesive mfgs.

sigh ... if only I could choose the installer, but we purchased the home from the builder, and we're stuck with the subcontractor that they used. I guess that's not entirely true ... we could have someone else do it, but we'd have to foot the bill.

Oh, I was able to get a look at the meter and it's a mini-Ligno (and I believe it was E/D model).


To see if I understand, let me rephrase the above: the flooring has acclimated to the environment if the moisture content of the flooring is 5%, and the ambient relative humidity readings in the home are at 25%. Do I have that right, or am I being dense?

Thanks,

Paul

Thats about right.

I have a mini-ligno as a back-up meter. It's not as sensitive IMO as my Tramex but does the trick.

Here's the species correction chart for the E/D on the second page.

http://www.lignomatusa.com/MoistureMete ... nualED.pdf


Oh, if they are testing a subfloor they should be using a hammer probe with it for different depths The pins on meters are not of sufficient length to get down into a subfloor.

IS the hvac up and running? If not then your acclimating it to the outside. I Hope your over a basement.