retain pre-1964 extension during renovation

old_house

Hi all,
we are currently in the process of buying a ~60 year old house in Kerry.
I understand that all building works done before the relevant regulations came into law do not count for the current exempted development extension limits (ie the space of an existing pre-64 extension is not taken into account when building a new extension today).
For that reason we would like to retain the existing converted garage at the side of the house and also build a new extension at the back which between them would exceed the exempted size but should be fine with the garage disregarded. The problem however is the access into the back garden during the works.

My question: How much of the old garage can be taken away and later rebuilt to still qualify as pre-64? We thought about taking the front and back walls out to create a way through, possibly even take the roof off which has to be redone anyway and just leave the side wall standing (the other side would be the outer wall of the house). Would that be permissible or would it create a new structure in a planning sense? The size and appearance would not have changed when everything is finished.
Thanks in advance for any opinions.

antiskeptic

A case of Triggers Broom?

Not being definitive but I've seen cases where someone rips out a terraced cottage, leaving only front wall and they construct a new cottage+extension. The structure is considered a new rather than refurb+extension.

A section 5 would be a way to find out.

old_house

Thanks, I know what it sounds like
I will ask the local council what they think. The point where my idea differs from the example you mentioned is that the "new" structure will be exactly the same as the old one and the only reason for any work will be to make a temporary entrance into the back garden.
Maybe just taking the front window + wall below out will create a large enough opening, while at the same time still keep the original structure sufficiently complete. The back wall already has a door and since it is at the back it might be less of a problem anyway. I want to do it by the book, hence the question...

old_house

Just to finish this thread: we did not find a way to legally keep the exempt status of the extension intact during construction, so we applied for planning to demolish and rebuild it afterwards. Granted with no problems, so everything is sorted now.