My understanding is that your can claim PPR on a house and one acre of grounds. The other limiting factor with PPR is that you can only claim its current use value (i.e. its current value when sold as a house with one acre of land and not, for example, as a development site for four houses).
Ya house and up to 1 acre. So the question is what is the 1/2 acre worth???? Depending on its location a 1/2 acre site might be worth €100k whereas a 1/2 acre field might be €5k.
If it’s the garden down to the road type then it’s probably field value.