Moisture level of wood seem low.

morrier · **Joined:** Thu Apr 21, 2011 11:49 pm **Posts:** 1

I'm getting ready to install some 2 1/4" wide Brazilian Teak over 3/4" OSB and bought a Lignomat mini-DX to make sure
the moisture content was within recommendations. The Lignomat is a pin type meter. The lowest reading the meter
can detect for both the Brazilian Teak and OSB is 3.5%. The wood has been in the house for a couple of weeks and both
the new flooring and OSB read 3.5 or less. One of the OSB readings said 4.0. Is that normal? It seems a little low to me.
Should I be concerned that the meter is inaccurate?
More details:
1: Hygrometer says house stays at about 40% to 50% year round (central air and force hot air heating).
2: Location: New Hampshire, 2nd floor of colonial constructed in 1995
3: Meter manual says that it is self calibrating.
4: If meter is turned on without any wood, it is out of range and reads 3.5%
5: If meter is turned on with fingers across the pins, meter reads 20%. Manual says it should read above 12% with that test.

KevinD · **Posted:** Fri Apr 22, 2011 9:18 am

sounds pretty low most meters wont read below 6%. Have you quit running the heat yet? At 40-50 rh at 70deg that floor should be a little higher closer to 7 or 8.

floormeintucson · **Posted:** Fri Apr 22, 2011 9:46 am

The chart (which will not copy) says solid @ 40% rh should average 7.7 , plywood should average 5.8 and OSB would be 3.6%

Quote:

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.

FPL Wood Book

KevinD · **Posted:** Fri Apr 22, 2011 9:50 am

man I hit it on the head without any chart. I think Ive about got this acclimation thing down.

floormeintucson · **Posted:** Fri Apr 22, 2011 10:07 am

KevinD wrote:

man I hit it on the head without any chart. I think Ive about got this acclimation thing down.

You sure did Kevin. :mrgreen:

But this is what threw me, he is getting the same readings for the Teak and OSB at 40% he should not be getting the same readings for both.

Quote:

The wood has been in the house for a couple of weeks and both
the new flooring and OSB read 3.5 or less.

Me thinks he needs a better thermohygrometer or something.

floormeintucson · **Posted:** Fri Apr 22, 2011 10:15 am

So taking into account the chart and this rule :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.

The average between solid and ply is typically 1-2% lower (ply being lower than solid) and OSB is showing a 3-4% LOWER difference....an OSB sub-floor will never be within the spec for plank flooring. Unless the rh is down at 10% and stays there. :shock:

According to the chart @ 10% rh OSB is within the 2% of solid (lower) , after it hits 20% rh the OSB is continously 3-4% lower than the solid.

Moisture level of wood seem low.

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