Filler is old, dried out and falls out easily

Q: We recently bought a Victorian farmhouse that has wide-plank pine floorboards. The boards have gaps that have been filled once, but the filler is old, dried out and falls out easily. I would like to re-do the filler, but I’m not sure of the best product to use.

Any recommendations?

Some gaps are quite wide, up to 3/8″ wide. I love the look, but it’s drafty on a windy day and I want to re-seal them.

A: I’ve use a number of wood fillers, but they all will crack and pop out eventually, especially so if there is movement between the boards. Even vibration can cause it to pop out. With one pine floor which had large gaps, I packed the gap with rags twirled like rope and applied some expanding polyurethane adhesive. (rope or other alternative could be used) After that dried, I sliced off any adhesive that expanded out of the gap and then filled on top with Timbermate which is a more robust filler. It is expensive and difficult to work with because you have to keep mixing water with it. No waste with the product though, which is one of the good things. Be aware that if you don’t plan to have the floors sanded, you will need to tape off the surface of the boards along the edges of the gaps so the expanding adhesive does not get onto the face of the board. One thing for sure in using this method: it won’t fall out and it helps to stabilize the boards against movement.

Related Q: We refinished an old wood floor. There were a lot of little gaps between some of the planks, so we filled them with wood putty, then stained and polyurethaned. Now we notice that a lot of the putty is popping up through the floor. What do we do? Can we sand what’s above floor level and re-stain and poly again? What do you suggest?

A: Which brand of wood filler did you use? The way this is suppose to work is the gaps are filled, sometimes more than once to bring it to the level of the floor surface or above. When it has dried this all has to be sanded off flush with the floor surface. Staining is done after this. If you are saying that the filler is now being pushed up this means the floor is expanding from excess moisture. This could be from high humidity or perhaps from water in the filler itself. You have already finished the floor. I think I would cut the excess off with a razor knife carefully, then buff and coat if needed.

Similar Q: There were gaps between some of the floor boards in my home, which a flooring company repaired with a wood filler. The filler has already cracked and it looks as if the edges of the hardwood floors have cracked with it. What is the best solution for this problem? How best to remove the old filler?

A: Gaps as wide as a dime are considered by the National Wood flooring Association to be normal. Of course, good climate/humidity control and proper acclimation of the floor before installing will go a long way to minimizing gaps. It should also be noted that some wood species are more susceptible to gapping than others.

From what I’ve found to date, all wood fillers will crack if there is movement between the boards. Removing it is tedious and may result in some chipping of board edges. You could simply run a thin screw driver inside the gap and suction out the pieces of filler. At times you may have to tap down on the filler to break it away from the board edge. A razor knife may also help in removal. Perhaps a better solution on larger gaps is to mostly fill the gap with an expanding polyurethane adhesive and when it cures, use wood filler to top up the gap flush with the floor surface. A word of caution however: Moisture can exert a lot of stress on a floor. If humidity readings and moisture readings in the floor are high the wood is going to expand and push planks over. After the moisture level drops the boards will shrink. A very strong side bond created by the adhesive could cause a problem called panelization where the floor gaps in sections. Best solution is to control indoor humidity or accept that floors are an organic substance and will move with the environment.