Crowning + severe gaps = lack of humidity control. Wood will tell you where the HIGHEST level of moisture is. It actually POINTS to where the humidity is HIGHEST. Crowning (where the center of the board is HIGHER than the edges) indicates there is more moisture ABOVE the boards than below. That means the BOTTOM of the boards are DRIER than the top. With in-floor radiant heat this makes sense.

The gapping also indicates the IDEAL indoor Relative Humidity is NOT being maintained. These seem to be rather wide planks. In the flooring world, "wide plank" is defined by any board that is 5" or wider. Wide planks are NOTORIOUSLY unstable.

So I can see several concerns going on here:

1. Relative Humidity (RH) MUST be maintained between 45% - 65%. This is the homeowners duty to ensure this range is maintained in perpetuity.

2. Wide(r) planks used in a home with low RH

3. In-Floor radiant heat is DRYING OUT the planks MUCH FASTER than a traditional "dry" climate and exacerbating the already difficult situation.

You *might* have recourse with the builder failing to build the humidity control into the homes heating/cooling system. To find out if you have recourse, you will have to move QUICKLY. The 1 year time limit has run it's course...but the builder may have given a longer time period. I don't have a great feeling about this one though.

I'm sorry but this will probably fall to you, the homeowner to rectify the humidity difficulties. I suggest getting a humidifier into this space QUICKLY and pump up the humidity to sit at 45% for a few weeks. See what happens.

If you see IMPROVEMENT...then you know EXACTLY what has happened and why. You can then call in an HVAC specialist to install a whole house humidity system for you.

Sadly the builder has used the wrong material for flooring over the wrong type of heating system in the wrong climactic environment. A REALLY good construction lawyer *MIGHT get you something...but probably not.

What is your indoor humidity during various parts of the year? The prescribed remedy for low indoor humidity is generally to have a whole home humidifier. What is the moisture level in the wood flooring? If the humidity and moisture level are too low, adding moisture to the air and subsequently to the flooring may solve may of the issues you have without having to resort to unsightly methods.

Well, I might as well weigh in. As a Northern California based manufacturer of hardwood flooring AND having had the pleasure of working in the Truckee/ Tahoe area for many years, I'm familiar with conditions.

However, as mentioned by others, it's difficult to jump in this late in the game. There are too many "variables". But in the interest of answering a few of the questions asked... NO that degree of shrinkage is certainly not permissible or standard. You don't specify the widths, but your photos suggest 2-1/4" Solid... please correct me if I'm wrong. Regardless, that amount of shrinkage affects the STABILITY of the flooring, as well as the aesthetics. Obviously, the greater the gap, the less contact between the tongue & groove, which is essentially what holds the floor together (unless it was glued & nailed, or glued only)... which brings about the next question regarding HOW the material was installed, and over what system?

There are a variety of possible causes, any one or combination of, can result in shrinkage & board distortion. The other fine folks have already outlined most of them.

It's been my experience that the term: "reclaimed" can be a mixed bag, unless you are 100% certain of the origin/history of the material, such as where it resided, how was it removed & then stored? Was the moisture content checked &/or allowed to "adjust" adequately before installation (acclimation).

Regarding the use of "an appropriate caulk/grout"... I'm hoping that's not the vernacular used by the installers, because that would suggest to anyone in the HARDWOOD floor business, that those individuals weren't experienced in the trade.

As suggested by the other Pros, anything done in the interest of filling the gaps, even if using an acceptable WOOD FILLER, would only be a Band-Aid fix.

As usual, most of us who are qualified in the trade, hate to come into a scenario such as this where some/most of the problems could & should have been avoided.

Situations like this never leave everyone fully satisfied.

Hello! Thank you, thank you for everyone's expertise and clear, concise advice. The floors are random sized boards from 3.5-7 inches in width. I do not know: if the boards are solid (although they appear to be for the laywoman's eye); the exact type of radiant system we have; how the floors were installed (glue, nailed/stapled or otherwise); whether the wood was acclimated; or whether it is solid, rift or quartersawn. After typing this I now know I really know very little!!! The humidity in the house appears to be 26%, which is very unofficial. I have no meters to measure the moisture in the boards. Yes, the words "caulk/grout" were used as the proposed fix but maybe it is because they were conversing with a non-professional, me. All of your expertise has given me an incredible amount of information to work with. If I could summarize at the simplest level (based on partial information) - it appears that the main cause of the gapping between the boards is lack of humidity at the installation site as well as incorrect materials for site, climate and heating system. That it would be prudent to test this theory with increasing the humidity in one room and if true installing a full home humidification system seems to be the logical course of action to create the proper environment for the materials chosen and heating system installed. I am still at a loss with regard to the crowning, but this issue is not as prevalent as the gaps. I will try to get the above unknown information from the contractor/floor installer so that an informed decision can be made, I hope they will be cooperative. Cheers!

26 percent is way too low. I've seen enough NWFA inspector reports to know that. At that low of a level your wood will eventually shrink so much that it will crack. You can debate whether the floor person should have advised about keeping the indoor humidity between certain numbers but the need to do so is undeniable. The sooner you rectify this issue the better. Even engineered floors can be damaged by persistently low humidity.

Crowning and cupping are caused by a difference between the level of moisture in the top of a board vs.the bottom of a board. I suppose it could also be affected by the grain orientation in particular boards exacerbating moisture differentials. As wood releases or absorbs moisture, it doesn't do so uniformly through the thickness of a board all at the same time. Bringing the wood to a stable moisture content may alleviate the cupping/crowning.

tahoeshack ...

Your flooring installer would (hopefully) own or have access to a moisture meter, although at this stage, one would think that had already been utilized. It was helpful for you to note the widths... that helps explain the degree of shrinkage. Obviously, the wider the board, the ratio of shrinkage due to drying out increases.

You may be in for a long ride... hopefully, you don't think by introducing higher humidity into the location, significant improvement will be noticeable soon. It could take months, or longer to recognize any results, even if they occur... and then you have to take into account the fact that the seasons are changing as well.

Hopefully, this doesn't become a "tail chasing" exercise, and you ultimately find a solution. Good luck.

If you think of it at a later date, please keep me updated... we're located in the Sacramento area, and situations such as yours are always of interest (although my preference is to address conditions IN ADVANCE to avoid issues like yours).

Drop us an update at: David@selecthardwoodfloor.com