Cracks in wall

[reno2025]

Hello,
Removed some wall paper to redecorate today, found hair line cracks on one side of wall , other wall has deep vertical crack ( this is an external wall)
Should I worry?
What trade person do I need to check / fix this?

 

[Wayners]

Concrete blocks with sand and cement then plaster?
1950s to 1960s built house?
Seen plenty of cracks like that.
Though to cavity cracks I filled with bolt resin.
Then I used ready mixed bags of mortar, fill the deep cracks.
Toupret powder fill over.

As for spider web cracks. Plaster skim walls with embedded plastering mesh. I bought that in 100m long rolls that are 1m wide.

 

[michealangelo]

Slightly thinned coat white matt allows you to see overall state of walls

Fill as above

Cross line walls

Bobs your uncle