I get one thats 2mm wide. The crack internal is about 2mm wide in summer, then in winter it comes together like too plates shifting creating a raised edge if you put traditional plaster/spakfilla in it now.

Its annoying as its caused by extreme weather conditions based upon reactive clay foundations.

I have a few other cracks just in corners of the plaster in one room, not major, just the foundation in extreme drought shifting a degree or so.

Is there a plaster filla that has some form of latex/stretch that I could use just a little to cover and paint over? Id rather a ridge in winter than a crack in summer when selling the house. Maybe Dap elastopatch?

I also have a fair few cracks along the plaster board seams/tape, at the top of the tape there is just a ridge line, Im thinking I can just sand that down flat and paint back over it? I have one that the tape is old and lifted and will replace with something like fiberglass mesh tape and fill, sand, paint etc.

Does resene have an elastic paints that can be used? In the bathroom I believe it is a hard bord not plaster, but between them they form hair line cracks, where an elastic paint would stretch. I can see where they have just rolled paint over it in the past to fill the hairline cracks.