Moisture level check prior to installation

[EllenEL]

I get the idea that level of moisture in the floor is important. Since I do not have and specific devices to check for it am questioning whether I need one, since my installation will be on a second floor over plywood/osb that been in place for years.
Even if I buy moisture meter and check my subfloor what will I do with those numbers?
I live on IL/ WI border and from my humidity monitor it fluctuates from 30% in the winter to 70% in the summer. I really do not like 70 so we get continous hvac fan and dehumidifier going on those days so most time we fit in 30-60 humidity area.

 

[C.J.]

I check everything because I have to document it for warranty and liability purposes but you should be just fine skipping that on a second floor. Concrete slab or a first floor is definitely worth checking even if you just get a cheapo moisture meter.

 

[Mark Brown]

What are you looking to install? That really will make most of the difference in if it matters at all.
I assume wood??

 

[EllenEL]

Yep, engineered wood. I bought some wood a while ago thinking that is where I start my remodel but then got "brilliant idea" to quickly update my master bathroom.
Plumbing ended up a disaster. So now few months later I am getting ready to finally put floors in. Wood has been sitting in my living room for 4 months.

 

[Mark Brown]

That is the ticket right there. For the most part, your greatest concern with wood is that they are all at the same moisture content, it is know as equilibrium moisture content or EMC. The EMC is the moisture content given for a specific temperature and relative environmental humidity. You can find them listed on charts and check against them with a moisture meter. It is how I "calibrate" mine. Typically we test for these things at the time of delivery and installation. Round these parts, Pacific North West, we are looking for something like a 7.4-8.2 or that is what I see the most anyway. The idea being that when you install a floor the floor will not absorb or release moisture into the subfloor and vice versa because they are the same. More than likely over that long of a time they are going to be just fine.

What does concern me is the very large humidity swings that are present in your environment. Wood likes to maintain a constant value and a 30% fluctuation is not very constant. That being said, my home does it too and in the winter I have nice tight wood and in the summer I have rather gapped wood, it isnt the end of the world and I am rather use to it. Short of investing a rather large amount of money to control this, there is not a lot someone can do and I typically suggest that people remember that wood is wood and move on with their lives.

 

[EllenEL]

Thank you for responses, I am very grateful to learn. Yes, wood will be wood, tight in summer and loose in winter. Humidity being what it is and our age what it is ... Unlikely I will be living in next generation of netzero housing with latest and newest tight controls over everything.
That said my BIL just build netzero house with all latest tech so I will get to visit.

 

[highup]

What Mark said is true about how the humidity affects the wood. You have another plus that you are using engineered wood. Depending on the number of layers, engineered wood floors expanded contract from what I've heard, at about 10% the rate of solid hardwood. It's simply more stable and it takes an awful lot of moisture to make it warp.

 

[highup]

Here, download this then go to chapter 12 and download that one.
Part way down the page is a list of cities in the United States and shows the approximate changes in Wood moisture content month by month. It's interesting to see the moisture swings in different parts of the country. Note cities along any coastal city. They have the least amount of swing or change during the year. Inland, other cities will go extremely dry and extremely wet with large swings in humidity.
This is the moisture content in the wood not the simple humidity in the air that you typically think about.
https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htmDownload this, then click on chapter 12 and go down four pages for the chart.

 

[C.J.]

If it’s Khars and it’s floating (as you mentioned in a previous post/ thread) then the entire floor will grow and shrink as one so I wouldn’t expect gaps n such as you would if it was nail down. I think you’ll be just fine

floating for the win

 

[Mark Brown]

This is the floating floor. That is correct.

You gonna be fine!

 

[Mark Brown]

I suppose my comment was not the most informative thing going but here it is in detail

The difference in moisture content from a sub floor and a floating floor is much less critical for a few reasons, namely that they are not connected. The reason moisture contents need to be about the same is really quite simple. The idea is that when the two surfaces are affected by changes in humidity for what ever reason they do it in tandem and matched. This keeps the structure from failing. Also, when it is first installed an imbalance could create either a growing or shrinking wood and the inverse on the subfloor. That spells disaster.

When you install a floating floor, the two will remain independent and not interact directly upon each other.