Gap between main house and extension (Victorian)

[O25]

I have a gap between my main house and double storey extension. Although I call it an extension I think it has been there since the house was built as every house on the street has the same layout. The gap is even all the way through and it is not wider at the top than the bottom. I wanted some advice as to how to rectify this issue. Do I need wall ties or wall pins? Or can I just fill the gaps in with plaster?

 

[KenGMac]

O25, firstly, I see this is your first post? hope the answers tendered assist?

Some Questions?
I assume the image posted is of a door between the main house and the Extension?
Is there doors on the ground and first floor, probably directly above each other, if so? do both ground and first floor doors have similar conditions, the gap?
Are there any vertical separation cracks between the outside rear wall of the main house and the extension?
Do you know what the plaster finish is on the wall between the extension and the main house, by this I mean the finish of the plaster on the extension side?
Are there any draughts emanating from the gaps?
And finally? in your opinion have the gaps widened at all during your ownership of the Property?

Ken.

 

[^woody^]

You need it looking at professionally, not thinking about wall ties or plaster.

If the rear wing is moving away from the terrace then you need to know why, and if it's ongoing or stopped.