First time poster and hardwood flooring newbie here. Thank you all so much for your posts, this website has been very helpful.

I have a question on acclimation. I just ordered 600sf of solid prefinished red oak, 3-1/4 wide, and plan on installing it myself in the coming weeks. I live in CT, and I have window unit AC's if that matters (no central AC).

When I ordered the wood, the salesperson told me that their company's installers strongly advise against opening the boxes and letting them acclimate to the room. He said to put the boxes in the room for at least 24 hours prior to install, and leave the boxes closed. He said the installers typically just open the boxes and check the moisture level of the boards, and then proceed with the install. He went on to say that opening the boxes would cause problems. He said they've been doing this for decades and installed gazillions of square feet.

Am I missing something? I thought I was supposed to open the boxes and let the wood acclimate to the room? After all...it's eventually going to need to come out and end up on the floor 24/7, right? Is there some trick about using the moisture meter prior to the install, that these installers are using?

My original plan was to open the boxes and let them acclimate for a week or so, make sure the moisture content was within 2% of the subfloor, and install...please let me know what you think.

I agree with the recommendation from the shop - this is because we are in the summer months and humidity is higher than normal. Acclimating the material to these conditions will mean its fat when it is installed. As the humidity decreases going into the fall and winter months, especially when you first turn your heat on, the material will dry out and shrink, leaving gaps between all the planks.

The material needs to be installed in the conditions the manufacturer states it will perform best in, typically MC of 2-4% and RH between 40-50% depending on the material. If your home is a constant controlled environment, and meets the requirements of the manufacturer, then you could proceed to acclimate the material if needed. However, if you home is too wet or too dry due to the renovation process, you should not acclimate the material, but install it as it comes from the shop (which SHOULD BE in the correct range if their warehouse is storing material correctly - this is why installers should always check MC and RH before install).

Best advice is to get a moisture meter and take your own readings and go from there.

Thank you WestonKris for your quick response. Makes sense and good insight on the specs. I do plan on getting a moisture meter.

Follow up question for you however... if I don't acclimate now, will I run into trouble next summer? In other words, won't the boards expand due to the humidity next summer and get fat and start to cup, if I install them at nominal width and flush board to board now?

It is a bit humid in my house right now at ~65%, and I don't run my AC all the time in the summer months.

I guess the alternative would be to acclimate now and live with the gaps in the fall/ winter. Or maybe shoot for the middle ground, and install in October? Surely some amount of gaps or cupping must exist due to humidity changes throughout the year...

Please let me know what you guys think.

No matter when you install, the material will expand and contract in response to changes in the humidity in the home. The idea with acclimation is that your space needs to be consistent all year round. It's ideal for a number of reasons to keep your home from getting too dry (less than 30% RH) or too humid (more than 60%) as you will run into problems with all the wood elements of your home, your drywall, etc. Swings in humidity can also create condensation in spaces where you do not want moisture to appear. Therefore it's recommended to aim for the middle ground all year round.

For your question re: expansion - when you install the material at the right MC/RH range, you'll be in the middle and yes, some expansion will occur during the summer months as humidity outside creeps inside. This is why you will be leaving a gap around the perimeter of the area, to allow the wood to push outwards instead of upwards. The gap should be the same as the thickness of the material, likely 3/4inch.

A dehumidifier can help keep the moisture down in the summer and prevent serious problems, and is more important then running the AC (which only drains some moisture in the form of condensate off the fan coil). Get yourself a cheap weather station or similar device to monitor your indoor humidity and turn on your dehumidifier when you see it creep up over 55%. You can even use the dehumidifier to bring your current site conditions to the manufacturer's recommend level for the install.

Remember - its about getting the site to the right conditions, not the wood.

An example of when you would acclimate material might be if your new flooring came from overseas in a container and picked up a lot of moisture on the way. You'd want the wood to breathe for a few days prior to make sure any excess moisture dried out (that's why we take readings daily). Alternatively, UNFINISHED wood that was just produced might be on the dry side coming out of the kiln. I think a lot of the acclimation misconceptions stem from the fact that previous decades saw a lot more finish on site material than pre-finished.

Thanks everyone, this is super helpful. Sounds like I need to run my AC more often.

I do have a dehumidifier running in the basement year round, with the thought that humidity (moisture) is heavier and ends up in the basement. I think I read that somewhere years ago. My install is on the 2nd floor... would you suggest I put a dehumidifier on that floor as well?

Ideally, at the time of install the flooring's moisture content should be at the annual average moisture content for your geographical location. That way the flooring will neither expand too much in the humid Summer months or contract too much in the drier Winter months. And as the other responder said the flooring will be happiest if the house's humidity level is maintained at the optimal range year round. The installers check the mc of the flooring and then install.......this assumes that the mc is optimal......what if it isn't, do they go home and come back at a later date? Where has the flooring been stored prior to delivery? Acclimation happens based on the relative humidity at its own pace and not based on a set amount of time. What's supposed to happen in the 24 hours the flooring sits packed up in your house? Company has to keep the installers working, so have the flooring delivered and send the installers in the next day. Can you get a copy of the flooring manufacturer's acclimation and installation instructions? Also, have the installers document the flooring moisture content so you will this info in case of a problem.

Depends on the RH reading on the second floor - if it's too high, then yes, a dehumidifier would help.

As Jim pointed out, the MC/RH range will vary depending on where you are in the world. I'm in Toronto, where we have cold winters with lots of dry heat and humid summers, so the RH can swing anywhere from as low as 20% up to 65%. This is why we aim to install in that 40-50% mid range. And we install all year round too, new construction, where you seldom have proper climate conditions indoors. Our installers pick up the wood the same day from our warehouse where we keep everything kosher, and install it like that. Then depending on the site conditions at the time of year, it may expand or contract; however, once everything is closed up and turned on for the homeowners, the climate regulates and everything typically returns to as it was when it went down.

Thanks again everyone for your help. I'm looking into dehumidifiers now, in conjunction with my window AC's.

I live in Connecticut, where the winters RH is in the ~30% and the summers RH is up to 100%. I did some researching and it looks like the average annual RH is ~65%. (At the moment, with hurricane remnants headed our way, my upstairs is reading around 80%.)

I visited the flooring shop yesterday to return some samples, and asked two guys there (different from the original salesperson I spoke to) about my install questions. They both repeated that I should leave the boxes closed............but that I should let the wood acclimate in the room/floor for a week. They simply said the wood would acclimate through the cardboard boxes (which sort of reconciles what the first salesperson said to me). In their very next breath however, they did say that I should try to have my AC on for several days prior to wood delivery and afterwards in order to better mimic average seasonal RH.

So I think...their counsel mostly correlates with what you folks have been saying to me.

Here's my plan, based on everything I've learned so far:
-I'm going to run my AC over the next week until the wood arrives, to aim for ~50%-60% RH (the average annual RH for my area).
-I'll get a moisture meter. The manufacturer states that subfloor should be between 6-12% MC, and that the boards should be within 2% of that reading during the install. Sounds good to me.
-During the install, I'll keep the AC going as needed in all the rooms to maintain the RH levels. I'm installing myself, and between work schedules and shuffling furniture around it's going to take me a few weeks to do it all.
-Next summer and forever after, I'll be sure to watch the humidity levels in my 2nd floor and AC/dehumidify as needed to keep it down.

Please feel free to offer any corrections to my plan...

What city do you live in? The annual swing in moisture content for Ct is 7 - 8%. Higher end for coastal locations.
Who is the manufacturer of your flooring? Red Oak flooring is happiest in the 45 - 55% relative humidity range year round.

I'm in the Hartford area. Not quite coastal.

The manufacturer is Superior Flooring. Solid red oak, prefinished, 3/4 thickness by 3-1/4.

Keep in mind that I'll do my best to keep the RH down in the summer, but sometimes I'm either cheap or lazy to put the window AC units in and turned on . That's why I'm thinking of shooting for the average seasonal RH.

I just went to the Superior Flooring web site. Very interesting. It seems that they do the acclimation at the factory and the boxes are designed to keep the wood at the factory acclimation and don't acclimate it in your house. They say that the installation site must be at the proper relative humidity range and kept that way year round. Interesting concept.

I saw that as well. I wonder if the boxes are sealed in plastic or something.

So... doesn't that should kind of restrictive? After all, I don't live in a museum. Between AC fluctuations, seasonal activity, my kids opening windows, etc it doesn't sound 100% feasible. I wonder if it's written that way to cover them in case of warranty claims.

Some installers will do the job and not explain to the home owner that the indoor environment's Humidity level should be maintained within a certain range year-round. These folks you are dealing with are being proactive and seem to be trying to ensure that the wood will be delivered properly acclimated and forewarning the customer to begin with a climate controlled site.
You can do whatever you want with the flooring i.e. re-acclimate and install at your convenience. I wouldn't worry too much about opening windows, etc.....when the humidity gets too high for the floor it will be too high for you too and you will turn on the A/C. Same in the winter....when the humidity goes down and the house gets dry and static-y you may want to turn on a humidifier. Get a temperature/humidity monitor and keep an eye on it so the RH doesn't get too far out of range.