Extension wall coming away from original house

[alice88tims]

Hi everyone,
See photos attached. We moved in to our home 2.5 years ago. The original building is around 100 years old and then the extension is approx 25 years old. The previous owners had issues with plaster cracking at the internal joint of new wall and old wall and they had it surveyed in 2013 and the surveyor said no external signs of movement. It has since started cracking inside again (got a lot worse after we had excess rain damage due to a slipped tile meaning the rain got in and then this very hot weather and drought has made it all much worse over the last 2 weeks) and I have now removed the plaster and looked at the outside wall and it appears to have a gap.
I know that a gap can be normal but it certainly looks slightly wider at the top than the bottom of the house.. is this a cause for concern? Should we be getting a structural engineer out to check for subsistence, issues with foundations, etc etc?
I'm panicking slightly!
Thank you very much
photo 1 - shows the cracks and which wall is the old building and which is the newer extension.
photo 2 - outside separation
photo 3 - after i took the plaster off

 

[Wayners]

Yeah. Get it looked at.
They will tell you what's happening and what you can do.

 

[^woody^]

It's not normal. You need to know what the cause actually is, as there are several possible reasons each with a different possible solution and some causes more urgent than others. You need a structural engineer