CU

[Angie]

We purchased 4 acres of farming land 5 years ago and obtained a CU for just over one acre of it.  We have built ourselves a house but wish to sell about a third of an acre as a building plot.  I realise that a building permit will need to be applied for any new construction but is it likely that the original CU will still apply or will this need to be renewed?  Assuming (as with most things in France) that if so, this will not just be a formality!  Thanks in advance for any help/info.