Here’s why

In Don’t mention the wall we drew attention to the difficulty inherent in planning legislation which requires us to take an original building into account, particularly if the relevant part of the original building no longer exists. 

An inspector deciding an appeal against the refusal of prior approval for a 6m ground floor single storey rear extension under Part 1, Class A of the GPDO in south-west London (DCS Number 400-033-147) provides an insight into the rationale behind that legislation. 

The inspector determined that the proposed extension would not be permitted development, reasoning that an existing rear projection created a side wall and was still applicable because it was part of the original dwellinghouse, even though it would be removed. Consequently, the proposed extension would extend beyond a wall forming a side elevation of the original dwellinghouse and have a width greater than half the width of the original dwellinghouse, and therefore would not accord with criteria A.1 (j) (iii).

In coming to this decision the inspector had regard to Arnold v Secretary of State for Communities and Local Government [2015]. The judgment explains, she related, that a limitation is to be read as stated, and supported that appeal inspector’s conclusion in relation to extending beyond a wall forming a side elevation. The court ruled, “Firstly, there is no caveat in the GPDO which indicates that if original walls are demolished then the limitations within it no longer apply. Secondly, if this argument were to apply it would mean that any amount of increase in width could occur, so long as other limitations, such as not being within 2m of the boundary of the curtilage (A.1(g)) were satisfied. On a large plot such as this it could lead to huge additions being added beyond the line of an original side wall simply because it had first been demolished. I cannot accept that this was the intention of the Government in the rights conveyed and, as I have already pointed out, I am reassured in this finding as this is not what the wording of the GPDO actually states. Consequently, I find that the increase in the width of the front projection is not PD and required planning permission.”

Section 4.3421 of DCP Online provides information on development within the curtilage of a dwellinghouse.