My kitchen floor sits on joints that are mostly OK. One wobbles though as I walk over it near a wall. It moves 0.5cm (0.25"). I lifted a floor board and had a look. You can see the crumbled mortar here:
Question: Do I replace the mortar after jacking up the joist a little? Or do I get a hardwood wedge and tap it in - as the joist goes out the other side and supports a narrow hallway?
The house was built in 1973 in the UK, if that's important. Lastly, it is my poor photography that makes the joists look non-vertical, not poor construction.
Here's the adjacent one that is fine for now:
The sub floor area is a crawl space - but only just - not for anyone with a belly. The black is a bitcuhmen seal over the earth underneath.