Solid Hardwood, Engineered and Laminate Flooring - Floor "grout" to fill in gaps between wood?

Hello,
We redid our old hardwood floor. Sanded and "polyurethaned" it One part of the house had soft wood with (I think) pine. It was not meant as hardwood floor, but still looks beautiful after we sanded it and put two layers of polyurethane on it.

I am in the process of adding two more layers of polyurethane to it. The problem is that there are sometimes up to 2/16 inches gaps between the floor boards. I was hoping the Polyurethane would fill it up, but it did not; there is just dirt collecting.

What products can we use to fill up the gaps? Wood putty seems to be a little difficult since it needs to be filled along the whole board, 10 feet sometimes. Is there any "wood grout" one can use such as you grout tiles?

Thanks,
Ben

Unfortunately, it's too late for this, but at least you'll know for next time. The normal process is sand all the old finish off, stain if desired, and then a fairly thin filler is dumped out of a bucket that color matches the wood as closely as possible and is troweled over the entire floor with a flat trowel. When it is dry the floor is sanded one more time to remove all excess filler leaving only what's in the imperfections, cleaned thoroughly, and then finish is applied. During the filler process the filler is pressed into places such as you describe. The whole floor is done because it's faster and there is little chance everything will be caught in a "do what you find" method. I'm not sure what the answer is at this stage unless it would be to sand the finish off the places you want to fill, fill them, redo the finish in those areas, screen the whole floor to even it all out, and then apply your additional coats. Hope I've helped more than depressed.

sht. thanks for your reply

what would happen if work with the thin filler at this stage? I have to screen off some of the polyurethane anyways and two more layers I want to put on. Is it impossible to get it better at this point? I mean right now I have gaps with dirt filled, how much worse cold it get? I was hoping to use a utility knife, get the dirt out between the wood, apply a thin grout. Maybe do some careful sanding with a screen. and then do two more layers.

That's kinda what I was suggesting. Having never done it myself, it's just guess work at this point. A real hardwood guy may have a better suggestion, but if it were my floor, I think I'd find an inconspicuous place to try it and actually sand off the two coats you've done so far in a small area. Then I'd scrape any foreign matter out of the imperfection, work in some of the filler, and let it dry. After it's dry, I'd sand it smooth, clean it good, and re-apply the finish. When that dries, my guess would be it's going to be a bit obvious where the new finish is, but should feather out when the floor is screened. If it looks like it'll work. it may be labor intensive, but you may be able to salvage the situation that way. I'd suggest doing it in a closet or something where you can shut the door later if you don't like it. If you decide to try it, let me know how it works.

just for conversation's sake, as i'm not a hardwood flooring pro, there have been previous posts on this subject and it has been said by a hardwood flooring pro that it is pretty much futile to fill these gaps with wood filler, because when the floor expands & contract, as it will, the filler will be pushed out & you'll be back to square one.

http://forum.doityourself.com/showthread.php?t=265225&highlight=wood+filler