I am in the process of installing 3/4" solid unfinished, and I am discovering the widths are not exactly the same. Most fall into 4.975 - 5.005, about a 1/32" variance. This seems like a bit too much, but I wanted to get an opinion here. A few are actually a lot worse than that, like 4.875", or each end of the same board can vary up to a 1/32". What's an acceptable variance for board widths? My plan was to measure every [damn] one of them and group them into ranges of widths (maybe 1/64" variance) and install all the boards for a row from particular group. Any suggestions?

What are you installing? Is it hardwood? Is it milled by an American or Canadian company? I have on rare occasions run into hardwood that was poorly milled but that was quite awhile ago. Nowdays, my distributors only carry quality flooring and if there are any reports of sloppy milling, they stop doing business with that manufacturer. It costs everyone big bucks to return badly made flooring. I will run into a board here and there that is a little skinny and try not to install those. Keep in mind finish in place floors are meant to be filled. But only the installer can determine if the amount of gaps is acceptable to him and will be able to be filled. If you are not happy with the milling job, don't install it. Just return it for a refund and buy your wood elsewhere.

This sounds like it was purchased at LL!

The tolerance is Zero, unless the wider boards have a higher moisture content. This is going to make a very gapped floor. Morning Star bamboo is the worst I've seen with that defect.

5% or less in unfinished is acceptable. Is this floor hickory or maple by chance? More than that and it's not your problem imo take it back for an exchange.

Floor is Ipe, unfinished, milled by an American company (South Carolina). They have been in business for about 20 years. All they do is mill unfinished flooring, decking, and moulding. I do have a few gaps on the floor (I did not realize what the problem was until I got half way through one room). Honestly, with some filling, I doubt anyone who has not installed wood would notice anything, but of course anyone who does install would if they closely inspected the floor. Shipping this back is probably not feasable, as I doubt they will pay shipping (1000 lbs across the country isn't exactly cheap). I guess I can contact them, but I seriously doubt they are willing to do anything. But maybe I am wrong. For the record, it is not LL!

I kind of expected unfinished planks to have slightly worse tolerances than say an engineered /finished product. But I'd still like to get an idea of what an installer might gawk at. If some of the boards vary by 1/32", would that stop you in your tracks and refuse the wood?

Thanks all for your help.

It sounds like you at least are going to be able to turn it around and thats what matters in the long run. I pretty sure i know who you are talking about and if it is give them a call. Most suppliers/ mills want to know if there is a problem otherwise they dont know any better unless they get some sort of feedback.

We learn from NOFMA that wood milled at different Moisture Content dries to different widths.

I am having the same problem with a solid Hartco Kempas floor. We have had 2 different sets of installers try to get it to lay without uneven gaps. The floor rep from Hartco claimed it was installer error. They ordered new wood & still are having the same issues. The floor was acclimated & we have the same humidity year round. The gap is about 1/32 now but we are afraid as the installation goes on it will get wider. Any advice? Should we accept it as is & ask for a price reduction or tell them to pull it up & go in a different direction? They are suggesting going with an engineered floor. We really like the Kempas look & the idea of a solid.

A virtical grain plank will not expand or contract as much as a flat grain plank when they gain or lose the same amount of moisture. If the flooring is 5” plank and milled when the moisture is at say 6% and it is shipped across the country and gains some moisture all the flat grain planks will be wider. Here in the humid south we see this all the time with wide plank flooring.
I guess this can also happen to 5” Ipe.