Multiple gaps running the length of the planks

Q: We purchased a new home in January (2 ft. of snow on ground!) The house had just had 3/4 inch thick x 5 inch wide oak pre-finished micro edge hardwood installed in an open floor plan: living room, dining area, kitchen and family room. This installation is above grade on plywood main floor, but with an unfinished basement below it (which is below grade and has a concrete floor).

No vapor barrier was used either underneath the oak flooring or on the ceiling of the unfinished basement. It looked great. Now in Sept., and a dryish summer (we’re in BC), the floor has developed multiple gaps running the length of the planks, that are wide enough to insert a 5 cent coin. What’s the best repair here?

A: Increase the humidity in the house.

Related Q: I recently purchased a house that had not been lived into for two years. The house is approximately eight years old. The floors were pine tongue and groove over what appears to be avantec sub-flooring. When the house was purchased the floors looked good, but had some of the finish flaking off. I had someone come in and strip and re-seal the floor prior to moving in. The work was done in Sept/Oct with no heating or air conditioning having been run for two years.

After approximately one month after the floors were done and the heating systems were turned on there are several boards in several rooms where the boards are cracking down the center of the board, and several other boards where the seams are coming apart. In the worst seam you can place approximately three quarters in the crack. These splinters and cracks between the boards were not there prior to the sanding and refinishing. Could it be that with the house vacant for 2 years that the boards had a high moisture content when the sanding and refinishing was done? How can this be remedied? I’m trying to find out what you think the cause could have been and what the possible fixes could be.

A: I would say the boards had a higher moisture content than they did after the heat was finally turned on. That is why they shrunk and gaped. Try to keep the RH in the home around 40%. Wood has moisture traveling through it all the time from it’s environment. The goal is to control how much. I don’t suppose the person who sanded the floor took any readings before sanding?

Second A (for some reason he answered the same question twice, and obviously had more time for the second go!): Pine is notorious for serious shrinkage. Now that heat if finally in the house the planks are shrinking. You can try to maintain a higher humidity level in the house. During winter months around 40% is ideal. You can’t go much higher than that, but don’t let it drop into the 20’s which is too dry. I doubt this floor will close up but it might be wise to wait until the humid summer to see what the floor is going to do. Then you could fill the large gaps with a polyurethane adhesive. There is a liquid form at Home Depot. You will have to tape the surface of the boards along the edge of the gap and crack because this adhesive will expand. After it has hardened, cut off the overflow to flush or preferably below the surface of the boards with a sharp utility knife and then use a colour match wood filler to apply on top of it. I suggest the moisture cure polyurethane adhesive because it won’t crack out.

Similar Q: I moved into a new condo about a year ago. The floors are floating engineered hardwood (non glue). They have developed small gaps at the seams, in different areas, at the top of the planks and at the sides. One was repaired in the past but the gap returned in the same place. Should this be happening? What is considered acceptable? Also, what do you suggest to repair the problem? Thanks!

A: I’m assuming these are click joint floors. It sounds like you have a low humidity issue. It must be significant to cause this gapping. Is it possible you have a hot spot in the concrete, perhaps from water pipes beneath?