I have a real similar project to shark's posted here, and I'm having similar questions and issues. 3 1/4" wide, 3/4" thick prefinished hard maple. It has been in my house for 5 weeks. The relative humidity has been 33% to 46% over the period. I have checked it daily.

Mostly stored in the boxes, although I took some of it out initially and tore the ends off many of the boxes.

I started opening boxes and laying it out to let it breathe last weekend, planning to install next week. I have about half of the wood unpacked, the rest is going to have to wait a few days. I checked moisture content of flooring and subflooring. The subfloors vary from 8 to 13, generally around 10-11. The floors vary from under 6 to 9, generally 6-7 or less. Ideally they should be closer together, right? Should I be concerned?

So what do I do to either "dry out" the subfloor or increase moisture on the floor? Would running a fan on the floor/subfloor to move the air around help?

Also, I found it difficult to get what I thought were reliable readings with the moisture meter. It is a Delmhorst J-lite, brand new. The maple is so hard that I can barely insert the probes without bending them. I already broke one of them, fortunately the unit cam with a couple spares. And the readings vary a lot, even in a given board. On one board in particular I read <5.5, 7, 6, and 9 within an inch of eachother on the same board. Sometimes the readings even vary when taking more than one reading in the exact same location. I am not sure I trust the readings. The subfloor readings seem to be more consistent.

Anyone have suggestions on using the J-lite meter?

Thanks.

To get a good reading you have to get the pins down into the wood. You can use two finish nails as probes to get a better reading, just drive them in about half way and touch the tips to the probes on the meter. Is this floor over a crawl space or basement? My guess it's over a crawl space and that might be one reason the subfloor is higher. If the floor has been in there for five weeks it should have acclimated to a closer reading. I would try to get them closer in MC before installing. Check what the floor joist and the sub reads from underneth, if it's higer on the underside then you may have to do something to dry out that crawlspace.

Thanks for your help, some responses:

"To get a good reading you have to get the pins down into the wood. You can use two finish nails as probes to get a better reading, just drive them in about half way and touch the tips to the probes on the meter. "

I will try that with the nails tonight and see if that helps. Some of the boards seemed harder than others. On the softer ones, I could get the probes all the way in but still got low readings.

"Is this floor over a crawl space or basement? My guess it's over a crawl space and that might be one reason the subfloor is higher. "

Basement. I guessed too that maybe the basement was damp and that was part of the problem. When I checked it yesterday it was 28% humidity in basement, vs 38% upstairs. The heat ducts are closed to the basement, so it doesn't get the moisture from the furnace humidifier. It is also 6-8 degrees cooler.

"If the floor has been in there for five weeks it should have acclimated to a closer reading. I would try to get them closer in MC before installing. "

How do I get them closer?

"Check what the floor joist and the sub reads from underneth, if it's higer on the underside then you may have to do something to dry out that crawlspace.[/quote]"

Good call, I will check this too. I expect it will be dry since the humidity in the basement is very low.

One other thing that just occured to me. We installed a new layer of 1/2" plywood subfloor over existing 1/2" ply, about 8 weeks ago. Glued (with PL-400) and screwed together. Could the glue be raising the moisture content of the wood? Or maybe it had a really high MC when installed and it's still adjusting? I guess if I check the lower level and joists from beneath and they are lowe, that will help me understand the issue.

Any other feedback is welcomed.

I checked the basement MC and RH. It is drier than the main floor. The joists are 6% or less. The bottom subfloor layer, measured from below, is generally 9% +/-. The humidity is under 30% in the basement.

I would guess it's higher in the summer. It is dry basement though, as the lot is sandy and there is a drain tile around the foundation.

Since your subflooring is 9% MC when checked from the bottom side, I think the problem you're having is the new plywood underlayment. For some reason, that is where the variance is coming from. It maybe that the adhesive you used was a latex/waterbased one that gave the underlayment a temporary spike in MC. That would also account for the different readings. As I see it, you will need to wait till the MC of that underlayment goes down. Using fans in the basement aimed up at the subfloor should help speed things along.

I think you're right Gary. I will try the fans. I am worried they won't dry things out in time. I mean they've been installed for 8-10 weeks already. How low do I need to go? My installation instructions say subfloor must be less than 12%. They are pretty close to that now. Most are 10-11.

At 12% with flooring at 6%, I think the differnence is more than would be ideal though. Maybe I'll put some fans/halogen lamps on the higher than 12 spots and see if I can get them down.

If most areas test at about 10%, you're almost there. I'll bet the underlayment as a whole was higher when it was first done. In an ideal world, with 3&1/4" solid maple, you would shoot for no greater than a 2% variance. I don't think you're gonna quite make that. But you will be close and if I were in your shoes, try the fans and the lamps for a week or so. Hopefully, that will make a difference. If not, it would appear you've done everything that can be done. So just install it and hope for the best. Be sure to flaten that plywood and use 15# asphalt felt under your flooring. Staples or cleats but staples hold better. Try not to overheat your home this winter and keep your interior RH up around that 40% area. Remember, you've chosen solid maple flooring. ALL solid wood floors will expand and contract with changes in temps and humidity. It's the nature of the product.

Hmmm?


With the interior of the home having rH readings in the low 30% zone, MC equilibrium should be in the 6 - 6.3%

With a higher rH readings of mid to high 40%, MC equilbrium should be in the 8 - 8.7%

I would check some of the existing wood work in the interior of the home to see just where equilibrium, actually is for your interior.

It does sound as if that plywood was really moist.


Are you using a pin type meter where you poke hole into the wood, or a surface meter, where you just lay it on the surface.

One thing you may consider is to "sticker" your wood flooring. It is a real pita. What you do is take all the flooring out of the cartons and stack it up in piles with "sticker" boards in between each row. The sticker boards need to be approx. 1/2" thick and not wide, maybe an inch. Put them every couple of feet. This allows the air to reach all sides of the boards. This is the fastest way to to get the floor in equilibrium with your RH.

Rack them out on that subfloor and flip them in a day or two!!

LOL!

Pin type - delmhorst J-lite model

I have most of it out of the cartons, laid out on the floors already, I will try the sticker boards to get more air flow. I have also been running a fan in the rooms where the boards are laid out to help move the air around the boards.

Did you try sticking some of the other existing wood work in the house, just to see what it says?

I checked other wood last night. There is an area which already had 2 layers of plywood subfloor, which we didn't touch. That is probably the best area for comparison. In 5 stabs they all read 9%. So it is dryer, but not by a whole lot. I took some more readings of the new subfloor. It is mostly at 10 I'd say. There are a few areas at 11 and very few at 12.

I also checked some moldings and other wood on the main floor. It was between 7 and 9.

Me thinks the subfloor is not going to get much dryer, and i need to get the floor boards up a bit. I will continue with laying them out and put a fan on them while keeping the humidiy up - unless someone has a better idea???

You could spread MVP and install the next day. I know it sounds nuts, but it will work. Its cheap insurance against moisture migration in the future too.