Hi,
We recently bought an old house (built in 1903) and are having quite a bit of work done to it before we move in. However, things are taking a little longer than I thought, the plan has changed several times, and we are spending money faster than I thought we would:) . I've done quite a bit of research regarding hardwood installation and the proper guidelines, but since plans changed at the house I no longer have what I would call an "ideal" situation. From the research I did, it sounded like the wood floor shouldn't be delivered until all of the wet trades are done. However, the floors were delivered last week and we still do have some wet trades to do. So, now my new goal is to wait until all the wet trades are done up on the second floor before we acclimate and install the hardwood on that floor. Then they will finish up the first floor and wet trades on that floor before we will acclimate the wood for that floor. Is that OK? Right now most of the wood is still in the boxes that it came in, minus a few boxes that we opened to look at. I also know from research that you're supposed to take a base moisture reading right after the wood is delivered. Unfortunately, that did not happen either. The contractor has a moisture reader, but it did not have Acacia wood as a species listed on his reader. I have now ordered a better moisture reader that has acacia wood listed. Once it arrives I plan to take a base reading. I also used a hygrometer a few days ago to measure the level of humidity in the house and right now it is at 25%. I know that that is on the dry side, although we have been experiencing pretty cold weather here in Pennsylvania. I'm looking into having a whole house humidification system installed to help get the humidity level up, but I do not know how quickly that will work . My main concern is do you think it's OK to install the Acacia solid hardwood flooring if the humidity level in the house is only at 25% ? Of course we would make sure that the moisture reading for the wood is stable and not fluctuating and is within the percentage that it should be. I'm just afraid of installing it in such dry conditions, only to have it swell once the moisture level goes up some .
Unfortunately, I feel like I am the hardwood installation expert (just from the research I've done) and that is scary because I have never installed a hardwood floor! It doesn't seem that the contractor usually uses a moisture reader or fully understands acclimating. Sorry for the rambling post. Any help or advice you can offer is greatly appreciated !

Fortunately it is possible to make an accurate prediction of the moisture content of wood in a relatively stable environment. It is based on science. You will need to know what species of Acacia you have to be as accurate as you can be. You may need to use spacers between the tongue and groove every so often to make up the gap page that you have, if the wood is too dry for the average moisture content over the year. Washers can be used then removed after several rows and then re-used, maybe e every 2-3 feet, depending on your calculations. The wood clan then expand without stressing the fasteners beyond their limitation when the outside air is ventilated into the house during the humid summers. without needing to keep an air conditioner running which lowers the humidity.

Ideal situation is to acclimate the flooring to the annual average moisture content and then install it. 25% humidity is too dry for the inhabitants or the flooring. Depending upon the humidifier you should be able to get the house humidity up in a reasonable period of time. The flooring moisture content could take some time to increase to the desired annual average, but as Pete A. said you could go the spacer route. There are charts that will tell you how much your flooring species will expand and contract with changes in the moisture content. But, you probably know all this from your research. FWIW your installer's intentions may be good but if he/she isn't working then he/she isn't making $.

Thank you for your replies! I'm wondering if I just need to find a more experienced hardwood flooring installer. I hate to insult our contractor, but do want the floors to be installed right.
I have looked for the dimensional change coefficient of acacia, but since it's considered an "exotic" hardwood, it doesn't seem to be easy to find this info.. So, in your opinions, we shouldn't acclimate and install the hardwood under the current conditions, unless we put the extra gaps in? The gap that is left around the baseboards wouldn't be enough to absorb the swelling?
Do you think I'd be able to find a local hardwood installer that would let me pay them to act as a consultant regarding the acclimation process?
Thank you!

If the flooring is installed too tightly in respect to the change in humidity, you will have cupping before you see any change in the expansion gap under the base board.
You may get advice from a wood flooring consultant.

Ok, thank you. I'm just wondering if I'm not able to find the dimensional change coefficient for Acacia, how will I know how much extra gap space to leave during installation? What if the gaps we leave are too much and the boards never fully tighten up so that there are always gaps between the boards? Or the other way around? Maybe I'm overthinking this. I will also try calling the manufacturer today to see if they can provide any info.. We are having a whole house humidifier installed next week and my hope is that it will raise the humidity level fairly quickly. We shall see.
I really appreciate your advice! Thank you!

This is another example of why Acclimation isn't as easy as bring "the wood in a few days before" and why my company stresses not acclimating the wood at all. We keep our warehouse at 45% year round so all our materials can be picked up and installed the same day. Then if the site conditions are too dry or too humid, it will expand or contract to the expected seasonal state after a day or two, but not fail as a result of being installed too dry or too wet. We do a lot of new construction, houses in the winter are heated with propane or gas temp heaters and its often too dry for an ideal install, and in the summer, houses do not have AC running and will be very humid - by not acclimating to these poor conditions we can still install without worrying about failure.

In your case, the remaining wet work might be a good thing if the house is sitting at 25% RH. The drying paint and tile mortar will had moisture to the house which might raise the RH enough for a decent install. If you are planning on installing a humidification system, then do so, get it running, and get the house up to 45% before installing the wood. That is the best advice. Once the house is stable, and the wood is acclimated to that stable range, your install can proceed as normal, without the need for spacers.

The perimeter expansion gap only handles the expansion for a few rows around the perimeter. As Pete A. said, if there is excessive expansion at the center of the room the boards will expand against each other and buckle.

Thank you, everyone! We will have the whole house humidifier installed on Monday and see what happens from there! I appreciate the help!