Extending a semi-detached house
Reviewed October 2026 · Not legal, planning or financial advice
The semi-detached suburban house is the most extended house type in Ireland. Most have a side passage, a reasonable rear garden and a straightforward rear elevation — which gives real choices.
The usual options
- Single-storey rear extension for kitchen/dining/family space — often possible as exempted development.
- Single- or two-storey side extension over the side passage — generally needs permission.
- Wraparound combining both — the largest ground-floor gain, with a permission needed for the side element.
- Attic conversion.
Choosing between them
If the brief is a better kitchen and family room, a rear extension usually wins on cost and planning certainty. If it is another bedroom, a two-storey side extension often beats a two-storey rear one because it keeps the garden and is less likely to overshadow neighbours — but it will need permission and must respect the street.
Matching the house
Many semis are rendered or pebbledashed with a hipped or pitched roof. A side extension that continues the roof and finish reads as original; a rear extension is where contrast (dark brick, large glazing) usually sits more comfortably.
Regulations and their interpretation change. This guide explains the position as we understand it in October 2026. Confirm what applies to your house with an architect, planning consultant or your local authority before relying on it.