Connected houses

[David H]

The only adjoining houses I've come across where you can gain access between neighbours is the old ones with a shared loft, and a whole terrace could be built with no boundaries through the whole roof space.

Out of curiosity, are there any other adjoining houses with internal doors, windows or other spaces that means some form of access between the two? I can't imagine a reason for it but doesn't mean it hasn't been done.

[john91]

Some small terraced guest houses have had internal communicating doors fitted to allow them to comply with the fire regulations, so that guests could have an extra means of escape via next doors stairs.

[bracknell]

I have a "flying freehold" with my property.  It belongs to me, but if my neighbour had to escape and could not do it from their property, they would have the right to go throught it.

[smorodina]

My two uncles owned houses next to each other and had a connecting door put in so that they had access to both houses.