How To Fill a Wooden Floor (video)

Depending on your preference, you may want to fill your floor. It can prevent drafts from coming up from beneath and it can help to make a floor look complete. Some people prefer to keep the gaps, they believe that filling the floor will make it look fake like laminate or lino. However, I would advice that you avoid filling gaps between really wide boards or pine floorboards, as the probability of the filler coming out is quite high.

[VIDEO BELOW]

When buying your filler, you may want to search on Google for a floor sanding supply shop near you. That way you can get high-quality filler, whether water-based or not. Alternatively, you can use PVA glue, or better (and cheaper), PVA glue watered down.

The reason I recommend using high-quality filler is that PVA, even when fully dry, tends to clog up the belts when you are sanding the filler off the surface (I’ll explain in a moment).

Before you start filling you should have completed the edge sanding to 50 or 60 grit and sanded the main body of the floor with at least 80 grit. I sand the floor to 60 grit, empty the dust bag, then sand the floor with 80 grit.

That way you have only fine dust from the 80 grit. But the advice I would give to a novice is also empty the dustbag at 80 as well, then do the 100 grit and use the 100 grit dust to fill the floor (and the 80 grit dust if you run out of 100 grit dust).

My reasoning for this is that the dust is finer, and it will be easier to mix and work with. Also, the filler must be sanded off the surface of the floor once it has dried. It’s easier to sand off the filler with 100 grit on a floor that has been sanded with 100 grit, before filling, than on a floor that has been sanded with 80 grit.

I hope that makes sense because now I am confused… and I’m writing it.

If you are sanding pine floorboards you may want to empty the edger bag before the 60/50 grit edge sanding and use that dust to fill the floor. Pine is very fibrous and even the 100-grit dust from the belt sander is not very nice to fill with. Edging dust tends to be a lot finer than belt sander dust.

Once you have your dust (and hoovered the floor). Get a small bucket or a painter’s kettle and pour some of the dust in. Then add a little filler (or watered-down PVA). Stir it with a filling knife or stick of wood or whatever.

Keep adding filler until the filler is quite viscous and moves very slowly to find its level after stirring. Then scoop it out and slop it on the floor. You can just use a decorator’s filling knife to fill the whole floor if that’s all you have.

Trowels like the one I am using can be found in builder’s merchants and floor sanding supply shops. You can also use a plastering trowel which is what I originally was taught to use. Scoop up a bit of filler and begin filling around the edges.

Slide the trowel back and forth almost snow-plowing it back and forth, as shown in the video. A fair amount of pressure is required to make sure you don’t leave excess on the surface. Go all the way around the edge and spiral into the middle of the floor. Once you’re done, scoop it up, throw away the excess, and wait for the filler to dry. The water-based filler should probably be left overnight before it’s sanded off.

Once the filler is dry it’s time to sand it off the surface with either 100 or 120 grit. Use the belt sander first and the edger second. (see: Why you should do the edge sanding last) If you found this helpful please let me know in the comments section below. You can also ask questions there, should you have any.

UPDATE: After 2 years of emails from US readers who cannot find this kind of filler, I have finally been given the name of a filler that is available in the US that serves the same purpose, and it can be found here.