Radon
A radon map colour worries you, and the surveyor did enter the cellar. Has anyone measured the radon in that house?
No. Nobody has measured the radon in that house on these facts. A map colour is not a measurement of this building, and a surveyor walking into the cellar is not a radon test. The survey records condition that was seen. It does not become a gas result because the cellar door opened. Do not treat the colour as a reading taken in the rooms. If you need a measurement, that is a separate test.
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?
Maps are published so people can see where radon is more or less likely across the country. The colour is about that mapped picture. It is not a detector left in the hallway, and it is not a result for the named house. Entering a cellar lets the surveyor comment on the floor, the walls, the damp and the access. Those comments use condition language. They do not record radon. No survey level guarantees concealed parts of the structure, and none of them quietly analyses the air. An open hatch is access. It is not a laboratory.
Keep the worry in the right file. If the colour is enough to make you want a proper measurement, instruct that measurement, or decide with your solicitor how it sits in the purchase. Do not write to the seller that the house exceeds a threshold. This note will not state one, because a colour and a cellar visit do not produce one. Do not write that the house is clear for the same reason. The honest sentence is short: the map was not a measurement, and the inspection was not a measurement either.
What should you ask your surveyor?
- What did the surveyor say about the cellar as a room, rather than about the air?
- Where did the colour come from: a map, or a test report with this address?
- What separate measurement would you need if the colour is not enough?
What are the typical next steps?
- Do not treat the map colour as a reading in this house.
- Do not treat the cellar visit as a radon test.
- Arrange a separate measurement if a measurement is what you need.
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
Does a darker colour mean the surveyor should have quoted a level?
No. The survey did not measure radon. A colour is not a level in the rooms.
If the cellar was NI, would that be a radon result?
No. NI means not inspected. It is not a gas reading either.