Old floors cop damage — water stains that go deep, boards that cup or crown from moisture, termite-eaten sections, or just planks that have split after decades of use. I pull the bad ones out and replace them with new timber matched to what's already there.
Once the new boards are in, the whole floor gets sanded back as one surface. You won't be able to tell where the old ends and the new starts. That's the point.
I source replacement timber locally where I can. If your floor is an older species that's hard to find, I'll track it down or find the closest match available.