Neighour's extension crack

[yeleek]

Hi,

On the left is my neighour's small extension, on the right is my Kitchen. Should I be concerned that this crack has formed over the last 12 months? Whilst the extension is new, the houses are terrace properties from 1900s. Any advice please?

Thank you

 

[motorbiking]

The neighbours roof appears to be trespassing. They should have build a parapet wall to stop the water draining on to your property, they appear to have cut in flashing in to your side. But yes it looks like the wall starter has failed (or not been used.)