In Nov 05 we removed all the WTW carpeting in our 1960's rancher to reveal original random length oak hardwood floors. A flooring specialist added new 3/4" oak in one room to match and complete the hardwood floors throughout the house in February 06. We then had the floors sanded and poyurethane finished.
In September 06 in the week or so when we had neither the heat nor the airconditioning on two boards in the dead center of the house tented up about a half an inch. At that juncture I noticed that a filler material(about 1/4" wide) was used as a spacer on the outside of one of those boards for about 9 feet. After the heat was turned on the tented runners collapsed and all seemed to be just an aberation of humidity during the fall. Now February 28, 2007 I notice that the runners allong that filler material are contracting to reveal a 1/16" gap. Some of the wood filler is fatiguing and lifting up under the vacuum cleaner. My worry is that when we turn the heat off and spring occurs with its humidity will I have more severe tenting and maybe splitting and should I just remove the filler and add new? The floors are over a casually heated/cooled crawl space.

If you live in an area with big humidity swings your problem will continue to happen as the wood absorbs and lets go of moisture. You want to try to create a more constant environment, so when you turn the heat on you should also turn on a humidifier. Once you get the movement under control then it makes sense to fill the gap and recoat the area.

JLC, Good prudent advice. I like the idea of controlling the moisture especially since we have forced air heat and the past winter has been very dry even for the lake community we live in. I'll monitor the humidity level before I have another lift up as I did in the fall. Thanks.

Hi Neighbor, You said your house is built on a crawlspace. What kind of floor is in your crawl? Some type of vapor barrier is a must! 6 mil plastic and 2-3" concrete slush coat is the standard.

Re the crawl space. a concrete surface covers the entire crawlspace. Vents are usually covered. There are two scools of thought on venting the crawl space and I have not ever found anyone who could provide a definitive answer to vent or not vent. In this South Jersey climate the small leak in the crawlspace ductwork seems to moderate the humidity in all seasons.