Badly bricked-up doorway

[sker51]

Hi, id really appreciate some advice. My Vic house has an old extension on it…. I think possibly the old outside toilet/ coal shed was joined at some point 50 odd years ago to the back of the house.
They rendered the new rear wall but not the side and an old doorway which was bricked up seems to be parting from the rest of the wall.
Is it possible to repair the ‘ gap’ if so, what with? Many thanks

 

[eon]

Do you know what mortar type is beneath the paint? If it's as recent as 50 years old it is probably safe enough to assume it is cement.
Without much more information I am assuming that the joint has cracked due to it's significant thickness. Beneath the arch it looks about twice as thick as a regular joint. You can rake out the cracked mortar joint and repoint it with lime mortar. To prevent it from happening again you could also bed in a row of "gallets". These can be stone or slivers of old slate. The purpose is to reduce the size of the joint and compress the mortar further. If repainting then ideally use something vapour permeable.

 

[sker51]

Hi, thank you that’s very helpful. 50 years is a guess I have to be honest…. The mains sewage went in in 1967 so I suppose I’m only working on an assumption!
Thanks again