Were you the owner at the time they did their extension?
Our neighbours house is owned by a housing association who are never going to do a side return, so we couldn't 'share' the boundary wall. If you or the previous owner did agree to share the wall then a portion of the boundary wall would be in each property.
If not you may be able to use their external wall and get all the space......
No I wasn't the owner, the neighbours built this a long time ago now.
The wall is up to the boundary, as in in place of a fence. Theres currently a lean-to on my side return connected to the wall where I would like to build a side return.
Try and dig out the planning from the council - it might show where the wall was built.
However you'll find out when you get a party wall agreement so you'll find out either way!
Were you the owner at the time they did their extension?
Our neighbours house is owned by a housing association who are never going to do a side return, so we couldn't 'share' the boundary wall. If you or the previous owner did agree to share the wall then a portion of the boundary wall would be in each property.
If not you may be able to use their external wall and get all the space......