What would constitute a substantial start to a building project?

[Mottie]

I obtained planning permission to build a 3 bed house on the site of a workshop I own a few years ago and I’ve done nothing. Trouble is, it expires this October. I understand that if it is started, that keeps the planning permission live. I’m not ready to build or sell yet so I was wondering what is the cheapest way I could technically make a start to prevent the permission from expiring? Would installing the drains be good enough - it would involve digging up some of the workshop floor and yard plus breaking into my neighbours manhole (He is currently end of terrace but mine will be when it’s finished) or perhaps even extending his drain to a manhole on my property. Surely the drains go in before footings? Any ideas?

 

[^woody^]

https://www.diynot.com/diy/threads/what-constitutes-commencement-of-works.466538/#post-3724824

 

[tony1851]

Drainage might not be regarded as a substantial start, as anyone could dig a trench and lay a pipe.
What would definitely count is excavating for foundations, and pouring and levelling the concrete; this is something which
is basic to the design of the building - drainage runs might not be.

 

[Mottie]

Ok thanks. Problem I have is that to do the foundations I have to demolish the workshop as the building will be the same footprint mostly. Currently the workshop has a single skin wall and probably 12” of foundation if that!