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Radon

Does a colour on a radon map mean the house is over the Action Level?

No. UKHSA’s Action Level is 200 Bq/m3 as an annual average in the home. UKradon’s maps show where a higher level is more likely. Darker means a greater chance. The map is not a measurement of the named house. The only way to know whether a home is above or below the Action Level is to measure it.

Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.

What is the fuller explanation?

A proper measurement, as UKradon describes it, uses two detectors, one in a bedroom and one in a living room, over three months. That averages short-term changes. A one-hour gadget on completion day is not that test, and a home survey cannot smell radon or see it.

If a result is over 200 Bq/m3, UKradon recommends the level is reduced. The Target Level is 100 Bq/m3, described as the ideal outcome of reduction in existing homes and of protection in new buildings. Between the two, reduction should be considered, especially if someone smokes or used to smoke. None of those figures is a remediation price.

What should you ask your surveyor?

  • Are you commenting on a map, or has a three-month test been done?
  • Does this house have a basement the map should not be used for?
  • Is radon inside your inspection at all?

What are the typical next steps?

  1. Do not treat the map colour as a rating 3.
  2. If you need a number for this house, commission the three-month test, not another general survey.
  3. Keep any later reduction quote separate from the survey fee. This page states no remediation cost.

Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.

Also asked about this

Is every house radon-free if the map is pale?

No. UKradon says every building contains some radon, usually a low level. Pale is not a measurement of zero.

Can the seller’s old test be used?

Only if you trust its date, its rooms and its method. A test from a different layout is not this house now. Ask your solicitor what was actually provided.

Sources