As gregmills_gw states...wait a full year. That will see an entire heating/cooling cycle. The summer months are often the puffiest time of the year for wood. The winter is the driest time of the year (in the Northern Hemisphere). I wouldn't get any more putty in there. There's a good chance it will look worse rather than better. Best leave it alone until you've seen a full year.

Your wood is changing to the new environment and trying to find a balance. You can help yourself out by keeping a close eye on humidity in the home. Your home may have a high-end HVAC that includes a humidistat. This is uncommon but if you paid top dollar for your HVAC system you probably have the ability to monitor the humidity.

If you don't have that system built in, then you will want to get a hygrometer from a home improvement store. If we are getting contraction in a wood floor in SUMMER time then it is very possible you will have to add humidity in winter. That means you have to get a good idea about your home's internal humidity levels. You will need to know where the floors are happy vs. when they really start to open up gaps.

Then you will have to find a way to maintain the "happy" humidity level. And to do that, you need to have some data and a method to correct low humidity.

Yes, I'd rather not do more filler, I don't think it looks very good where they did the filler last week. My GC and the flooring sub looked at it today and are proposing to replace a few boards in the problem area, then stain and refinish. I'm concerned with how this will look with only refinishing a patch.

What would the fix be if there is a problem a year from now? I know a different flooring person who did a great job on another project, and maybe I would just pay him to fix it if it remains an issue. But if the fix is expensive, then I want to hold my GC and current flooring guy to take care of it.

If nothing gets worse I'm OK with the current state. The drawback with waiting is that the flooring sub hasn't been very responsive AND my GC is going to work for another contractor, so I'm concerned that a year from now I won't have the leverage to get anything fixed.

I'm confused at why this has been such an issue with the new floor when no cracks in the existing hardwood floors (I have oak in several other rooms that I'd guess are at least 10 years old). I use the a/c and heat, but we're in a relatively temperate, dry climate so probably use less climate control than the average US household. Is it unreasonable to expect the new floors to be "happy" like the old ones?

A dry climate = gapping. It sounds like you may need to increase the humidity (which is part and parcel of 'shrinkage' in wood). The new floors will be as happy as the old ones. You simply have to wait it out.

Remember: the OLD floors went through the same concerns...but it sounds like you weren't around when they acclimated. Some floors take several years to sort themselves out (this is how it worked in the early to mid part of the 20th Century). Sometimes it took a full sand/refinish before the floors looked "happy". If you weren't around to see the acclimation/movement, then you would not remember what it looked like after just a few months.

I would not want to see anything 'replaced' or 'fixed' when these are freshly laid floors. You will simply be replacing one plank for another. The replacement plank needs to acclimate for a few weeks, it has to have the moisture measurements read to ensure it gets to the right level. You have to be willing to deal with this acclimation while you live in the house.

Please check with your installer and ask about acclimation (both length of time AND moisture readings). And while you are waiting for them to return your calls, go ahead and take several humidity readings per day....for about a week. Get an average.

And the GC is YOUR contact not the subcontractor/flooring guy. Whomsoever you paid DIRECTLY is your contact. It normally works this way: You pay GC and the GC pays the subs. Therefore you only contact the GC...not the flooring guy.

The GC/flooring guy is responsible for the physical laying of the floor. The HOMEOWNER is responsible for the INTERNAL living conditions. If you live in a dry climate, then you will have shrinkage such as you mentioned. Increase the humidity to healthy levels and this will probably go away.

Let us know the humidity readings you have been getting - it's the best way to figure things out.

Thanks for helping me understand. Would you mind clarifying a bit what you wrote here?

I would not want to see anything 'replaced' or 'fixed' when these are freshly laid floors. You will simply be replacing one plank for another. The replacement plank needs to acclimate for a few weeks, it has to have the moisture measurements read to ensure it gets to the right level. You have to be willing to deal with this acclimation while you live in the house.

I understand you're saying not to replace anything now (honestly that's a relief because it's hugely disruptive not being able to use the floor!). When you're talking about the replacement plank--is there a point where you would recommend replacing something?

I got a humidity reader this afternoon; it's been at 35-37% this afternoon. My google search seems to indicate that's on the dry side of normal, but I'm interested to know what you guys think.

I'm working through my GC for everything, the flooring sub isn't very responsive to him. Which is why I'm worried it'll only be worse a year from now :(

Thanks for all your help!

35% to 37% is definitely too low. Speak to an HVAC specialist to determine what you can do to raise your humidity to a more reasonable level.

I would only consider board replacement as a last resort. You'll lose parts of your t&g construction.

Some more numbers:

• Mon morning : 48%
• Mon afternoon: 45%
• Tues morning (today): 50%
• Tues afternoon: 47%

Saturday was a record high here (107 degrees), with just a little relief on Sunday (98 degrees) when I saw the 35% humidity, so probably the most extreme temps we get.

How responsive would the floors be to the humidity? (I still see the crack now with 47% humidity)

Thanks again for everyone taking the time to educate me!

What's the outdoor humidity? With temperatures like that I must assume you are in an arid area. I'm in Florida where the heat is somewhat limited by the humidity. If you have a hot day with the a/c working hard and an already dry air condition, you have to expect it will be even lower indoors. I've read about solutions to add moisture to indoor air in hot, dry zones.

Hardwood likes to sit as close to 50% as you can get it. It has an "allowable" range of 40% - 60% (roughly) but the 50% - 55% is ideal.

When it comes to expansion and contraction, a single humid day won't do much. It took months for the first small gaps to appear - which means it will take the same amount of time for them to disappear.

That means you need to sustain 50% humidity for a few months before you experience the visible benefit in your floors. Remember: you are in it for the LONG HAUL. Wood takes time to LOSE moisture which means it takes time to grab moisture.

Get the humidity up to 50% and then leave it there for a few months....then see how everything is going.