I get called in to inspect probably twenty to thirty solid hardwood floors each year that, after several weeks or months, have started to break open. A quick reminder: solid wood flooring planks are each one piece of wood, while engineered wood planks are several different layers of wood glued together, much like plywood. Every once in a while I see an engineered wood with gaps. In any case, it is a serious and very expensive problem. If you take the time to read the rest of this article, you can be sure this won’t happen to you, I promise.

“Moisture levels” are very important with hardwood floors. All wood has some amount of moisture. When solid wood flooring has been installed, especially if it has been nailed or stapled, and then begins to open at the seams so that there is space between adjacent boards, it is because they have shrunk. The only other possibility is that your house has expanded, but I’m pretty sure that never happened and never will. So why did the boards shrink? Because they lost moisture since they were installed. When wood dries it contracts, when it gets wet it expands. Ok, now we are getting to the most important part.

Most people are familiar with the term “acclimatization.” Most people know that wood floors, even laminate (such as Pergo), need to acclimate before being installed. Usually the instructions say to acclimate for 48 hours, or 3 days, or whatever, and then install. THAT IS NOT RIGHT. If you acclimatize the product as directed by the manufacturer for the appropriate time, then install it, and then open it, the manufacturer will not guarantee or replace it. The fine print in flooring installation is this: When the installer installs the floor, they agree that the floor and subfloor are suitable for the installation. The problem is that sometimes wood flooring appears in the house to be acclimated to a 15% humidity level and needs to be installed in a house with the subfloor having a 6-9% humidity level. There’s no way the floor could acclimate to those conditions in a few days. It will still be too wet. And after you install it, it will shrink and cause gaps. And worst of all, the flooring will have to be torn up and thrown away. It is not a correct situation.

I need to insert a little point here. “Some” gaps in solid wood floors are very normal, especially if you live in an area with real seasonal changes like I do in Eastern Washington. Our homes here will invariably be drier in the winter and wetter in the summer, which will cause some minor gaps and is perfectly normal. A sure way to tell if the gap is normal is if it disappears each year during the wetter season. But the gapping I’m talking about is not like that. A lady showed me how some spaghetti that had fallen on the floor had rolled through the holes. Or if you’re missing one or more of your favorite pets, that’s also a clue.

THE SOLUTION So before this horrible scenario happens, be sure to do the following before you install your new floor. The soil should be checked for moisture with a wooden meter. There are pin (invasive) and magnetic (non-invasive) meters, either of which will work. However, these cost anywhere from $200 to $300 or more. Insist that the installer have it checked for moisture, especially since it will be a BIG problem for the installer if you have gaps later. Because you know what’s going to happen? The manufacturer will send to me To look at the floor, I will take many measurements of dimensions and moisture levels, and using the coefficient of dimensional change tables in the Wood Manual, I will be able to determine what the actual moisture level of the wood was at the time of installation. I will find that it was too much. high (or WAY too high), and the finding will be that the hardwood flooring was not acclimated to the normal home environment before it was installed. OH! That will cost someone a lot of money and it will cost you at least a lot of hassle with replacement etc. You don’t want that, and neither do I.

By the way, engineered wood definitely needs to be weathered as well, although some of the manufacturers don’t want the boxes to be opened for weathering and some do, so pay attention to that. Also, laminates (which are real layers of wood similar to engineered wood except for the top layer which is melamine (aluminum oxide or similar) must also be weathered, but I have never seen a claim rejected because the floor was not weathered. For Laminates and many engineered woods are typically “floaters” meaning they connect together and become a single unit Any dimensional changes do not normally cause gaps, but rather a change in the amount of gap free space (perimeter expansion space) on the walls These topics will be covered in another article.

IN SUMMARY: With any type of wood flooring, but especially solid wood, make sure wood moisture levels are within 2-4% of the subfloor the floor will be laid on. In my part of the country where the relative humidity of houses is usually between 25% and 40%, the flooring must be between 6% and 9% before being installed. That leads to one of my favorite lines, “IMAGINE WITHOUT GAPPING!”.