Short answer: Check the EPA radon map for the Eircode: if the grid square is a High Radon Area (1 in 5 homes or more predicted above 200 Bq/m³), ask the seller in writing whether the house was ever tested and what the result was. Houses built after July 1998 in those areas should have a radon barrier. You cannot test before you own it (the test takes three months), so budget about €50 to €60 for the kit and, if the result is high, €1,500 to €3,000 for a sump and fan.
Radon is a gas from uranium in the ground. You cannot smell it. It gets into houses through floors and builds up in sealed rooms, and the EPA puts about 350 lung cancer cases a year in Ireland down to it. It is also one of the few risks with a clear map and a cheap fix, which makes it a line item rather than a reason to walk away.
The map
The EPA radon map divides the country into grid squares and predicts, from measurements, the share of homes in each square above 200 becquerels per cubic metre. A square where 1 in 5 or more are predicted above is a High Radon Area. Large parts of Galway, Mayo, Kerry, Cork, Wicklow and Carlow are in it. Dublin mostly is not. It follows the rock, so it can change between two towns ten kilometres apart. We read the map at the centre of a thousand towns: radon by county and town.
The 1998 rule
Since July 1998 new houses in High Radon Areas must have a radon barrier under the floor, and every new house must have a standby sump. So a 2005 house in Tralee should have a barrier; a 1985 one will not. Ask for the certificate of compliance if the house is post-1998. Barriers fail if they were badly laid, so a test is still worth doing.
Testing and fixing
The test is two detectors left in place for three months, then posted to a lab. About €50 to €60 from the EPA or a registered lab. You cannot do this before you own the house, which is why the question to the seller matters: was it ever tested, and what was the result. If the answer is a number above 200, ask what was done. Fixing an existing house usually means a sump and fan (€1,500 to €3,000) or improved ventilation for marginal cases.
The report reads the EPA prediction for the exact Eircode square and checks the build year against the barrier rule, then puts it beside flood, BER and the other checks so you see which one actually matters for that house.
Questions people ask
- Is radon a reason not to buy?
- Almost never. It is one of the few hazards with a cheap test and a reliable fix. Treat a High Radon Area as a line in the budget and a question for the seller, and as a point in negotiation if the house was never tested.
- Does a new house in a High Radon Area still need testing?
- Yes. The barrier is a membrane laid during construction, and a badly laid or punctured barrier does not work. The EPA recommends testing every home in a High Radon Area regardless of age.
- Does radon affect apartments?
- Much less above ground floor. Radon enters from the ground, so ground-floor and basement units matter; upper floors rarely test high.