Can my neighbour build up to my boundary in Ireland?

Whether a neighbour can build right up to a shared boundary depends entirely on the type of structure. Garden sheds, garages and similar domestic outbuildings can, under Class 2 (formerly Class 3) of Schedule 2 to the Planning and Development Regulations 2001, sometimes be positioned close to or on a boundary, but the exemption sets specific height limits nearer boundaries and requires that a minimum area of private open space remain in the curtilage. A boundary wall or fence up to a certain height is also commonly exempted, subject to conditions in Class 9.

For a house extension, the position is different. While a single-storey rear extension can be built as exempted development up to certain floor-area limits, most local authorities' development plans still expect reasonable separation from a shared boundary to protect neighbouring light and privacy, and any extension requiring planning permission (because it exceeds exempted thresholds, is forward of the building line, or is two-storey) will be assessed against those standards during the application process.

If a structure genuinely fails to meet the conditions of the relevant exempted development class — for example, because it exceeds the height limit close to the boundary — it is not exempt and requires full planning permission, at which point neighbours have the normal right to make a submission.