Radon Barrier in Ireland — Where It's Needed, What It Costs, and the Carlow-Wexford High-Risk Map
On this page
Radon barrier mandatory on every new build in Ireland since 1998. €8–€15/m² footprint. Carlow, Wexford, parts of Wicklow: add a sump.
A radon barrier is mandatory on every new build in Ireland since 1998. The standard is a 1,200-gauge polythene membrane, sealed at all joints and turned up at the slab edge. Cost: €8–€15/m² of footprint. In high-radon areas (Carlow, Wexford, parts of Wicklow, plus localised spots in Galway, Cork, and Tipperary), the engineer will also specify a radon sump — a 200 mm pipe through the slab connecting to a void beneath the membrane. A passive sump costs almost nothing to install. An active sump with an extract fan (€300–€500) is added when the post-construction radon test shows elevated levels. 1 in 10 Irish homes has elevated radon; in Carlow and Wexford, it's closer to 1 in 4. EPA Ireland publishes a high-radon map by county.
TL;DR
Radon barrier is mandatory on every new build in Ireland since 1998. 1,200-gauge polythene membrane. €8–€15/m² of footprint.
High-radon areas (Carlow, Wexford, parts of Wicklow): add a radon sump and an extract fan. 1 in 10 Irish homes has elevated radon.
Most new builds go with a passive sump (no fan) and a switched fan when the BER test shows elevated radon. Active sumps are cheaper to retrofit than a new membrane.
When this matters most
You're at design stage and specifying the foundation.
When this doesn't apply
The slab is poured and the membrane is under it.
Frequently asked questions
Do I need a radon barrier in Ireland?
Yes, on every new build since 1998. 1,200-gauge polythene membrane. Cost €8–€15/m² of footprint. In high-radon areas (Carlow, Wexford), add a radon sump.
Where in Ireland is radon highest?
Carlow, Wexford, parts of Wicklow. Localised high spots in Galway, Cork, Tipperary, and parts of Limerick. EPA Ireland publishes a high-radon map by county.
How much does a radon sump cost?
Passive sump: nearly free (a 200 mm pipe through the slab). Active sump with extract fan: €300–€500 installed. Most self-builders install a passive sump and add the fan if a post-construction test shows elevated levels.
Sources
EPA Ireland, Radon map and guidance. https://www.epa.ie/
Frequently asked questions
Do I need a radon barrier in Ireland?
Yes, on every new build since 1998. 1,200-gauge polythene membrane. Cost €8–€15/m² of footprint. In high-radon areas (Carlow, Wexford), add a radon sump.
Where in Ireland is radon highest?
Carlow, Wexford, parts of Wicklow. Localised high spots in Galway, Cork, Tipperary, and parts of Limerick. EPA Ireland publishes a high-radon map by county.
How much does a radon sump cost?
Passive sump: nearly free (a 200 mm pipe through the slab). Active sump with extract fan: €300–€500 installed. Most self-builders install a passive sump and add the fan if a post-construction test shows elevated levels.
When this matters most
You're at design stage and specifying the foundation.
When this doesn't apply
The slab is poured and the membrane is under it.
Where to go next
Branch into
Adjacent decisions at the same stage.