gaps in my floors – my fault or the contractors


I had #2 oak flooring installed last fall over 800 feet of my house. I am troubled by gaps (wide enough to stand credit card up in) that have developed in multiple instances between two boards. It is random throughout the 3 rooms rather than in an area. The installer and wholesaler came out and after looking blamed me the owner stating that keeping my heat at 64 degrees was the major cause and that to fill the cracks would be trouble as the fill would bulge out when it got warmer.

The wood was onsite almost three weeks prior to installation and I feel they are shining me on. Prior floors I have had and those of my friends haven’t exhibited the number of or scope or the gaps I am faced with. I live in the Seattle area which is high humidity in the winter. How can I differentiate between bad workmanship and natural processes?


Dear Jim I’m familiar with the weather in Seattle. I have a sister in Port Townsend, and I’ve lived on the the West coast the first half of my life. The outdoor winter weather has little to do with the way your floors behave, unless they were incorrectly installed. And temperature affects wood almost not at all. Wood being a hygroscopic material, will gather moisture from surrounding air and material until it reaches an Equilibrium Moisture content.

Now that all said, if you have a crawl space under this floor and your subfloor is less than 1″ thick of plywood, you can get moisture incursion from under the floor. If the crawl space is damp this can happen winter or summer. But during the winter when you heat the top of the floor these slightly expanded floor boards will shrink back into place leaving gaps. Most folks leave the indoor air far too dry for wood floor to behave well in the winter. Next time you go to a museum, you will see their hygrometers pegged at 50% all year round. So the ideal in a home (in any climate) is to have the indoor relative humidity range from 40-60%. Avoid the swings of 30% or more.

The installers did what they were supposed to. Except they did not inform you of these facts. And hey, you paid them right, why am I doing their job ? The EMC of the wood that was brought in was probably between 9-12% (I’m guessing this, check a local wood shop). Your area has a specific range of EMC that indoor wood has to have before it is installed as flooring an other solid wood products. If you were to complain against this company you would have to prove that the EMC of the wood was too high. But then the effects of which you speak would have happened the very first winter heating season. When you allow this EMC to go up during the summer or late fall when you wish not to heat. The finished wood slowly rises in it’s MC and settles once it reaches that new equilibrium.

Then in the late fall you throw the heat on one day a bake the floor to desert dryness. Now you can imagine what’s going ot happen. If this floor has not warped by now you are lucky, and you must have a heated basement or crawl space or very thick subfloor. And as long as the floor was nailed down, and not stapled, the wood and nails can handle this movement, and by spring the floor will begin to swell up and most of the cracks will disappear, but not all. Never fill a floor until the Spring, and use a colored latex filler that matches the floor finish. Best not to fill at all. I’ll explain later about the filler if you wish.

Oh, by second grade you mean I hope select and better grade, not the knarly Common #1 or #2. These lower grades do cause their won problems.

As always your Most humble servant, Joseph, the Wood Floor Doctor.