Every wood floor in Des Moines opens up in January and closes again in June. That part is normal. This is how to tell the normal kind from the kind that means something is wrong.
Wood is not inert. It takes on moisture from the air and gives it back, and it changes size when it does. Des Moines swings from around 70 percent relative humidity in July to under 25 percent indoors in January, once the furnace has been running for a few weeks. That is a bigger swing than most of the country sees, and a wood floor feels all of it.
A 2¼ inch red oak strip loses a few thousandths of an inch across its width when it dries out. Multiply that by forty boards across a room and the gaps become visible. Nothing has failed. The floor is doing exactly what wood does.
Seasonal gaps share three traits. They appear across the whole floor rather than in one place. They are roughly the same width everywhere, usually thin enough that a dime will not stand in one. And they close on their own by late spring without anybody doing anything.
If your floor does that every year and has done it for a decade. It is a healthy floor. Filling those gaps in January is the single most common mistake we get called to undo, because whatever you push in there gets crushed or pushed out when the boards swell back in June.
One wide gap in an otherwise tight floor is a different problem. So is a gap that does not close in summer, a gap that runs along a wall rather than between boards, or a group of boards that have separated together while the rest of the room stayed shut.
Those usually point to one of three things: the floor was laid at the wrong moisture content and has been moving ever since, the subfloor underneath has moved, or there is a moisture source below, which in Des Moines almost always means the basement. Most houses here have one, and an unconditioned basement puts moisture into the underside of a floor all summer.
If the gaps are even and seasonal, run a humidifier through the winter and keep the house between 35 and 50 percent relative humidity. That narrows the swing and the gaps get smaller. It will not eliminate them and no honest floor company will tell you it can.
If the gaps are uneven, the fix is not filler. It is finding out why the boards moved, which means a moisture reading of the boards and of the subfloor before anyone decides anything. A floor should sit at 6 to 9 percent moisture content in this climate. If it reads outside that, the number tells you what the problem is and filler only hides it.
Do not judge a floor in January. It is at its driest and its worst. If you are deciding whether a floor needs work, look at it in May, when the wood has come back and only the real problems are still visible.
Diagnosing whether the movement is seasonal or a moisture fault. $250 – $700 to dry and re-flatten one room.
Yes. Every wood floor in Des Moines gaps in winter, because indoor humidity drops under 25 percent while summer sits near 70. Even gaps that close again in spring are normal and need no repair.
As a rough test, a seasonal gap should not hold a dime standing on edge. Wider than that, or a single gap much wider than its neighbours, is worth a moisture reading rather than filler.
Not in winter, and not if they are seasonal. The boards swell back in spring and push the filler out or crush it. Filling only makes sense for gaps that stay open year round, and then only after finding out why.
It narrows the swing and makes the gaps smaller. Keeping the house between 35 and 50 percent relative humidity through winter is the single most effective thing a homeowner can do. It will not close them entirely.
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