A: I think the glue/fine sawdust mix would be worth a try! I have seen the filler get squeezed upward only once, on my own floors! It was only slight however, and did not detract from the look of the floor. How about trying this: Do the glue/dust mix, but make sure it is packed into the gap below the floor surface. After the initial rough sanding, a latex wood filler is applied to the entire floor, and sanded off when it dries. A more important factor, in my opinion on having wood filler be successful, is eliminating movement between the finished floor and the sub floor. There is a device one can purchase from the big box building stores (I have seen it once, but haven't tried it personally) which attaches to your drill. After drilling a pilot hole through the floor, over a joist, you then ream down the provided screw which is set below the surface, and then the head snaps off. It can be used with some success for floors with a lot of movement, and it only leaves a tiny hole. It is true that wood does expand and contract depending on the climate. Good climate control in the home will eliminate this situation, maintaining relative humidity to between 40-50 percent. That means possibly adding a humidifier in winter and dehumidifier in summer. Central air can help also, but not everyone likes central air.

