The short answer
Radon potential varies with local geology. Official maps identify where elevated indoor levels are more likely; individual home measurements are still needed to establish actual exposure.
Why risk varies from place to place
Different rock and soil conditions affect how radon is produced and moves through the ground. Broad descriptions of a county can conceal substantial local differences. Use official mapping for the actual property area.
Properties in the same street can differ
Floor construction, openings to the ground, ventilation and how rooms are used affect the concentration indoors. An attractive, renovated or recently built home is not automatically free from radon.
Use the official maps
UKHSA publishes radon Affected Area mapping. Its address search gives a probability report for a specific property. These tools support the decision to test; neither replaces a radon measurement.
Do not overlook below-ground rooms
A cellar or basement can warrant measurement even outside a mapped Affected Area. Consider how the space is used and follow UKHSA’s guidance for occupied underground rooms.
Sources & further reading
UKHSA: official UK radon maps ↗UKHSA: measuring radon in homes ↗Checked 13 September 2026. General property guidance; use the original source and seek professional advice for your circumstances.