There is a Bord PleanÃ¡la decision on a referral which might shed some light on this question. If you google 11 Bramble Court, Tramore you should find it. I haven't time to read it fully now but the bit of the report which refers to whether a development was to the rear of the house reads as follows:
(a) Is this an extension â€œto the rearâ€ of an existing house?
It is stated by the Authority in its initial letter to the referrer of 13th December that the extension is on the â€œpublic road sideâ€ of the dwelling and is therefore not covered by the exemption classes. The referrerâ€™s agent argues that there is only one â€œfront wallâ€ of the existing dwelling, and that is the front elevation that was so shown on the planning permission drawings, facing out onto the residential estate road. He submits that there cannot be two front walls. He also argues that there is no mention of a â€œpublic road sideâ€ in the Regulations.
I am forced to agree with the referrer. There is no mention, in Class 1, of any â€œroadsideâ€ elevation or â€œpublic road sideâ€. The Class refers only to an extension â€œto the rear of the houseâ€. Other Classes in Part 1 of the Schedule (for example Class 3 at condition 1 and Class 4 at condition 3) refers to â€œthe front wallâ€ of a house. The terms â€œrearâ€ and â€œfrontâ€ have to be given their commonsense meanings, in the absence of specified definitions, and the presence, or absence, of a public road is not a relevant factor in such an interpretation. (I understand that the corresponding UK Permitted Development provisions allow for minimum distances to a â€œhighwayâ€, but no such provision exists, or can be interpreted as existing, in our Regulations).
I consider that, if it had been intended by the Minister/Oireachtas to prevent any rear extension being exempted development in circumstances where a public road runs to the front and to the rear of a house (as in this case), then the Regulations would have explicitly included such a provision, perhaps as a further Condition and Limitation in Column 2, or else would have defined the exemption in another way, rather than stating â€œto the rear ofâ€ the house. The fact that the area to the rear of the house is described as having â€œprivate open spaceâ€ in condition 5 would imply that the open space has to be free from public view, not that it is between the rear wall of a house and a road. In the present case, the rear garden is indeed hidden from public view, by the screen wall (see photographs).
I also accept the point made by the referrer, that what was approved as a front elevation in the relevant planning permission, in 1998, has to be seen as the â€œfrontâ€ of the house, and that a Planning Authority cannot unilaterally change this, when dealing with an exemption.
Accordingly, I conclude that the proposed extension is to the â€œrearâ€ of the house, and that there is no provision in the Regulations in relation to an extension not being exempted when it is to the â€œpublic road sideâ€ of a house.