Ripples / chatter in badly sanded floor

Q: Our house was built in 1988 and we are the 2nd owners. When we moved in about 16 years ago the wood floors looked great. Then we had some boards warp due to water damage so we had them replaced and had the floors refinished; kitchen, living room, bathroom and dining room. We moved out for a week and come back to floors that had ripples everywhere, ripples in hardwood floor – in the wood, not finish. In the light they are clearly visible across the floor.

The company apologized and said the sander machine was defective and they would redo. We moved out again and come home to the floors the same. The company again apologized and said they would redo. We said no and found another company. They said they would fix the ripples by sanding on an angle and that would get rid of them. We moved out and came back to the same ripples. Another apology and said they would redo. We said no. 12 Years later… We want to have the floors refinished, but how do we get rid of the ripples?

A: This condition is called ‘chatter’. They did have a problem with their machine. The only way to get rid of them is to first sand on about a 20 degree angle to flatten the floor. This will have to be done again hopefully by someone whose machine is tuned up. May I ask what the spacing is between your floor joists? Some homes were built with 20″ or wider centers and I’m just wondering if you have a lot of vibration in your floor. Are you sure your floors can be sanded again? They have already been done 3-4 times.

Similar Q: I sanded a floor and have chatter. How can I fix it?

A: Assuming there is no finish on the floor you have 2 options. Use a polisher and hard plate with sandpaper discs (80 grit) and grind the heck out of the floor or sand again, initially on a slight angle to flatten out the chatter. Why do you think the chatter occurred?

Another Similar Q: I recently had oak hardwoods sanded and refinished by a professional contractor. Although the floor feels very smooth and shiny, it has very visible “ripple” lines when under light. The contractor redid the work, thinking the sander may have caused this. Same result. Any ideas on what is causing this?

A: This is called chatter. It is caused by the machine, but can be a vexing issue to find out exactly what the reason is. A floor not nailed well enough? A bad pulley or drum? The wheels may be slightly out of round? It re-appeared the second time probably because once these ripples are in the floor, you would have to initially sand on a bit of an angle to flatten the floor and remove them. Otherwise, the floor machine will simply follow the contour (ripples) and probably make them even more pronounced.

Related Q: We recently refinished a wood floor. After work completed, we noticed areas of visual rippling (i.e. the floor is completely smooth but visually there appear to be ribbons in the finish). Any idea as to the cause? Remedy?

A: It sounds like ‘chatter’. Have you ever bought lumber and notice areas on the wood where there is a ripple? Probably caused by vibration. These would be very closely spaced.