Radon Barrier in Ireland — Where It's Needed, What It Costs, and the Carlow-Wexford High-Risk Map
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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.
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.
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
Next decision
The next step in your build sequence.
- Foundation Depth in Ireland — 900 mm, 1.2 m, or Below Frost Line →
- Foundation for a Timber Frame House in Ireland — Raft Is the Standard →
- Piled Raft Foundation in Ireland — For Peat, Made Ground, and Soft Clay Sites →
- Raft Foundation in Ireland — The All-Rounder for Class 3–4 Ground and Subfloor Insulation →
- Subfloor Insulation in Ireland — PIR, EPS, or Mineral Wool, and What Part L 2022 Demands →
Branch into
Adjacent decisions at the same stage.
Watch out for
Common mistakes, hidden costs, gotchas.
Compare with
Alternative approaches worth knowing.