Damp - diagnosis, suggested solution please

Hi - wondering if someone can help with this.

See attached pic of an outside wall, to the front of the house. Seems to be sucking up moisture. Inside, there is damp in the wall, manifesting in wallpaper coming off. This has been on-going for a few years.

During summer, I bought some roof & gutter sealant, mended the gutter overhead and pushed some into the cracks in the mortar (you can see the black stain). Only a half assed job as my gut was telling me I would probably need to re-do the mortar properly.

Anyhow, just wondering if there is enough information here to suggest a solution for the dampness in the walls. The house is semi d, on the common wall with neighbour, in the hall, there are also signs of some damp. Same in the neighbours house.

Longer term plan is a renovation job, one optional item on the list is lifting the boards, cutting back the joists, and backfilling to remove any future concerns about rot/damp/rodent/draughts etc. This kind of thing makes me think it's a good idea, also gives the ability to see what's going on under the floor boards and in the wallss and deal with it properly.