Stabilising an extension from inside?

[jazzcricket]

My elderly parents had an extension erected on the back of the house about 25 years ago. One side wall, is continually cracking and opening up,where it abutts the original back wall of the house.
I had a look but you can't get decent access to it from outside,as theres about a foot of space to the fence.
Is there anyway,of tieing it in from inside. I was thinking chase out some channels in the extension wall, and try and drill into the original back wall, and put a bar with resin in it, then replaster the channels.
Is this feasible, or am i barking up the wrong tree?

Any advice appreciated.

 

[^woody^]

It would seem that the extension is moving because of the ground or foundation, and if so, ties may not be enough to hold it

Is this seasonal movement or a ongoing (continually widening) crack?

 

[jazzcricket]

Hi woody, i think the problems been made worse recently, with nearby trees being cut down, i think they call it heave. One in the neighbours garden,about 5 ft from the extension,and also 2x 100ft trees about 35 feet away on a playing field.
the terrace in the garden is definitely moving as well. It could well need underpinning really,and they are on a steep hill.
I'm really looking just for a way of stabilising the problem, so i can redecorate,without the crack appearing every few weeks,as my parents will be moving this year

 

[^woody^]

Damage caused by neighbouring trees would normally be claimable from whoever owns them. This should apply to NI, but I don't know about the south.

Heave damage should eventually stabilise, but it could take years. In the meantime, you may have to wait as movement would not stop

Would it be possible to form a flexible joint with plaster joint beads?