Hot Topics: Filling Gaps in Hardwood Floors

finished wood flooring with a sealed gap between planks

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Original Post: Filling huge gaps in hardwood floors

Gangnam - Member

I have a 1905 house in Boston with hardwood floors which have large cracks in them that were filled many years ago. In many areas the filling looks pretty good however over the years the filling in some areas had is cracked and crumbled away. I decided to refill some of these areas and have dug out the filler. I'm wondering what would be the best choice for filling these areas given that it is in fairly high-traffic areas. To make things worse, the floor boards are not entirely stable in the affected areas which surely explains the old wood filler cracking. I realize that probably the better option is to remove all the flooring and replace it however that is not financially feasible.

I've used the Elmers water-based filler in other areas of the house and it had good results however and none of these areas have been on the floor. I also wondered about the long-term durability of the Elmers wood filler.

To put this in perspective I will be selling the house in about six months and need to repair the floor for showing the house. Therefore I'm looking for a solution which will be reasonably durable and also pleasing to the eye.

Main questions:

1) recommendations for wood filler to fill a gap 1/2 to 3/4 inch wide, 1/4 inch deep? Brand-names specifically would be helpful. I'm considering water-based wood filler but would also consider epoxy or urethane based if someone can give me a good reason.

2) Staining recommendations?

3) Finishing recommendations?

4) any easy tips for stabilizing floorboards?

I will post some photos shortly.

marksr - Forum Topic Moderator

Welcome to the forums!

Is the gap only a 1/4" deep or is that all you are concerned about filling?

With gaps that wide, I'd consider ripping strips of wood to fill the void.

Gangnam - Thread Starter

That is a good idea although the spaces are somewhat irregular. The spaces are about 3/8 to 1/4 inch deep and I plan to fill them entirely. I suppose I could rip something to fill most of it and do the rest with wood filler of some sort. Looks like pine right?

Below is what I am dealing with and what I have already for possible fillers. One picture shows damage that must have happened before the steam radiators were repaired as the area has always been dry on my watch. The Stain pen matches the other areas that have been filled. My plan as it stands is to fill the gap, sand it, use the stain pen and then put some finish over it.

wood floor with gap between planks

wood flooring with gap between boards

wood filler blending pencil

wood filler product package

wood filler product in a small can

marksr - Forum Topic Moderator

IMO anything that reduces the need for more filler is a good idea. I wonder if taking a skilsaw along with a straight edge [fence] for a guide would allow you to put in a straight filler piece without as much filler.

Looks like pine to me.

Gangnam - Thread Starter

Are you suggesting that I use the skill saw to make the filler or would you use it to make the space in the floor more even (or both)? Seems reasonable but I am concerned about matching the color of the wood.

stickshift - Group Moderator

Mark is suggesting replacing the wood—using a filler piece of wood in the gap and using the saw to create straight lines so installing the new piece is easier.

marksr - Forum Topic Moderator

That's correct, make the gap even so a ripped piece of pine can easily be set in place. Set your saw blade depth at the same thickness as the flooring so you don't cut into the floor joist. Some of your gaps are really too wide to be a good candidate for filler. Inserting wood more or less guarantees that the filler won't fail [if still needed] and will look better than just using filler.

bish80 - Member

You don't happen to own an oscillating tool like a Fein multimaster or one of the inexpensive knockoffs.... because this is the reason to go out and get one.

(Here's a FEIN Multimaster on Amazon if you're interested)

I say, spend the money and you will figure out all sorts of other uses for it. It is the right tool for this job. The blade is less than 1/16th of an inch thick and you will be able to cut out a piece without damaging the next plank over. You can probably also buy a piece of floor that would match your grain pattern or at least the age on eBay, just type in pine flooring.

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