Hi all,
I’m a custom home builder in Charlotte, Nc. We seem to be running into an issue more than we have in the past and hoping for some advice. Our site finish floors seem to be gapping much more. We do sealed crawlspaces (some conditioned, some not), insulated foundation walls, no floor insulation, I-joists floor system, advantech subfloor, screwed and glued. We predominantly use solid 3/4” white oak floors  #1, sometimes select. 4”-5” wide boards. Depending on clients budget, we either seal the subfloor with a moisture sealer and use aquabar underlayment or we use a moisture glue. Always nailed down. Floors acclimate 3-4 days prior to install. Floors are installed during construction without conditioning. Finished after we turn hvac systems on for a week or 2. Crawlspace humidity controlled with a dehumidifier and set around 45-50. We historically have not humidified our air. Our issue is once it gets cold and dry we run into gapping. I know some is to be expected but we have run into more significant gapping in the past few years (up to 1/8”+) and it doesn’t fully cycle back in the high humid summer months.

My thoughts (for what they are worth): the sealed crawl is something we have adopted in the last few years. It’s great for a dry crawl but is it too dry? We also used to insulate our floor systems prior to this. Now just foundation walls. Does this have impact? I know the wider the plank the more shrink ratio but I also know that there are far wider than what we install. Should we humidify our air in the winter months (Recently we had a cold spell with highs in the twenties for a few weeks and humidy sat around 23% in my personal home). That would be the cheapest fix. i would love to do only site finish engineered floors but that doesn’t work with the majority of our customer’s budgets. 

I would greatly appreciate any and all suggestions. Especially if you build in this climate zone. I hope someone sees something glaring that I could improve. Thanks so much.