Cure a Popping Floor
This Old House general contractor Tom Silva troubleshoots a popping floor
Two years ago, my daughter had engineered flooring glued down over a concrete slab that had minor dips and waves. Now when she walks on the low spots, the floor pops. Can we fill them in without removing the floor? —Joe Harris, Boston, GA.
Let me first say that no flooring does well if installed over an uneven surface. It's well worth taking the extra time beforehand to fill the low spots with patching or leveling compound because it saves headaches and repair time later on.
You can stop the pop without removing the flooring by using a polyurethane wood glue, such as Gorilla Glue. This type of glue foams as it cures, so after you inject it underneath the flooring it will fill the space.
To make the fix, first drill a hole or two through the floor near the center of the areas you want to fill. Each hole should be just big enough to fit the bottle's nozzle. Next, bore a shallow recess for a wood plug at each hole, taking care not to bore all the way through the flooring. You can make your own plugs out of scrap flooring; you just need a drill and a plug cutter. Or go online and buy matching plugs at BearWood.
With the wood plugs close at hand, squirt a generous amount of glue into the hole at the bottom of each recess. Immediately stick a plug into the recess to keep the glue from bubbling out. Wait 24 hours for the glue to cure, then put painter's tape around each plug to protect the flooring while you sand the plug flush. Dab some finish on it to match the rest of the floor, and remove the tape. That should hide the repair and keep the floor quiet.
— This Old House general contractor Tom Silva