Internal leaf cavity wall crack

[misterp2811]

Hello,

I've lived in my 1950s semi for just under 5 years now. Throughout this time there has been a couple of cracks in the spare room (back wall of the house that meets the party wall) visible through the wall paper. Nothing was noted in the full survey I had done back when I purchased it. I haven't noticed it get worse in that time.

This weekend I've started to decorate the room and removed all the wall paper, on doing so I've discovered the crack is much worse than I thought and I'm now unsure as it if I should sleek professional advice.

The house is cavity wall with flintlock concrete guttering. There is no sing of the crack on the outside wall at all or on the same wall as it progresses into next door.

Should I be concerned?

The crack:

https://www.dropbox.com/s/epwhgckyujut912/Photo 31-08-2014 15 17 59.jpg?dl=0

https://www.dropbox.com/s/p1duiqfayo5ubqd/Photo 31-08-2014 15 18 04.jpg?dl=0

The wall from inside:

https://www.dropbox.com/s/clj85olfbw84477/Photo 31-08-2014 20 34 30.png?dl=0

The wall from outside:

https://www.dropbox.com/s/t7x7eel4c8ei90q/Photo 31-08-2014 20 34 44.png?dl=0

 

[tony1851]

Possibly the roof pushing outwards on the inner skin?
Are the ceiling ties in position, or has the roof been altered internally in any way?

 

[misterp2811]

I forgot to add one important bit of information, there is a loft conversion about (done in the early 90s from what I know).

I don't know if or what modifications were made to the roof internally, as far as I know none were made, but I can't be sure.

The ceiling joists run to meet that wall.

 

[tony1851]

The fact that the crack runs between the two cills (which is a point of weakness) suggests that the section of wall between the two windows is being pushed outwards at the top.

 

[misterp2811]

Thanks for your reply - It makes perfect sense.

Would i be therefore best to contact a building surveyor to get a full inspection of the cracks and their advise on how to address them?

Thanks

 

[tony1851]

If it has been cause by roof work, it may not necessariliy be on-going, but if you're not sure, maybe best to spend a few quid to get it checked properly.