We are renovating the hallway floors in my old apartment, and am running into a splintery patch I am not sure how to deal with appropriately. The floor boards are pine, 115 years old, about 30 cm (12") wide, 7m (20+ feet) long. In the middle of the middle board, the board was an unfortunate cut compared to the grain, and is delaminating (?) creating splinters. We still have to see how large an area this is a problem over after further sanding, but it will be at least 60 cm (2 feet), and up to 1.5 meters (5 feet) long, around 5 cm (2") wide. Pictures attached for reference.
Replacing the entire board is not really an option for practical reasons (time, cost, finding a matching board, damage to the remaining boards in the process), and replacing an entire section of the boards, coming with two cross cuts, would significantly affect the look of the floor.
I do have some shorter comparable floor boards from the kitchen, and so I was considering putting in a Dutchman patch, maybe even with tapered edges to smoothen the transition between the patch and the board. My main concern is how well such a large patch would hold up over time, with movement of the boards, in particular due to use. Any tips or recommendations on how to approach this? In particular how deep should the patch go for structural reasons? Should I fix it in place with some screws as well? The boards are about 3cm (1 1/8 ") thick, so there is some room in that direction.
I should also mention that we are intending to oil the floors, but could consider PU lacquer if this is a huge practical improvement.
Thanks a lot!
[I am aware that some boards have separated far enough for the tongue to have come out of the groove, but trying to take out the floor and laying it fresh is too much work and would likely damage the other boards too much.]
Edit/update: in the end, taking out and relaying the entire floor was not feasible given time constraints, as well as the likelihood of irreparably damaging the very long boards. We also did not want to affect the look of the overall floor by replacing a section. As usual, this ended up being a rushed job before a hard move-in deadline.
Beyond the particular problem I described, we fastened the boards with extra screws since they were creaking, we patched tongue and groove cracks with strips of new pine since they were too large. After the final sanding stage, the problematic area was still splintering. To "fix" this I glued down any separating bits that were not sticking out, and used pine-colored wood filler to even the edges out, to help prevent further splintering. I then gave it a final sand. The entire floor was finished with Osmo polyx natural, which contains a small amount of white pigment, to closely approximate the look of untreated wood. A year in, we have no issues with splinters (at least in what used to be the most problematic looking area!).
Below I include an image of the original spot, and an image of the overall floor (don't get distracted by the dust etc., haven't cleaned in a while!). In detail the spot certainly does not look perfect, but it is hardly noticeable in the floor over all (and that's coming from me, very aware of the existence of the spot). The pine filler is too light, and often too uniform, but blends in reasonably well given the new pine strips in the grooves. Given more time I might have done things differently, but I am fine with the current result.
Btw, I used scraps to experiment with glue and sawdust mixtures, as well as epoxy. I found glue and sawdust not suitable for a surface treatment like this, because it is difficult to get flat and difficult to sand without it overheating and darkening. Epoxy unavoidably seeps into the wood and darkens it, which is not a look we wanted.