My upstairs hallway is 23' long and one of its sides has no doors on it, meaning the baseboard on that side covers it continuously. I am using 1x6 poplar for baseboard and the longest piece my local lumber yard sells is 16'. I was thinking of joining two pieces but I don't want to have a visible transition.
The one idea that comes to mind is to biscuit join the two pieces or dowel them somehow. I also wonder if it would be better to just route a groove along the 6 side of each plank in the middle (so approximately 3/8" from each edge) and insert a joining strip of some sort that is elongated (i.e. looks like a popsicle stick). Once the joining and gluing is done, sand it really well.
Does one of these approaches sound right or is there a better way? I am sure there must be a way to fabricate really long baseboards from smaller pieces with a seamless transition.