Retaining planning permission

If you obtain planning permission and just put down the raft/foundation - will this hold the planning indefinitely or push back the planning expiry?

Coming at this from the angle of buying a site and keeping it until funds available to fund it fully.

Its a while ago now but I'm almost certain I asked this question some time back and was told that the fact that the foundations are down does not extend the period of the planning permission. AFAIK you must finish the house.

Anyone else have more definite reply?

I think the local authority require the property to be substantially completed before they will entertain any extension.

mf

Planning permission is usually valid for 5 years in which time building must be "substantially completed" in order to extend, as mf1 rightly said.