Radon
Can you use the ordinary radon map for a house with a cellar?
UKradon says not to use the maps for basements, cellars or underground sites, and to treat those as a higher chance wherever they are. A pale square on the map does not clear a cellar. A home survey that entered the cellar still has not measured radon. Measurement is the three-month test, not a look at the map and not a sniff at the air.
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?
Cellars are closer to the ground gas. They also confuse damp, ventilation and timber comments, which are separate from radon. The surveyor should deal with what they could see: damp masonry, rot risk, whether they entered. Radon stays invisible. Approved Document C is about resisting contaminants when building work is done. It is not a result for this cellar.
If people will sleep or spend time in a basement room, say that when you commission a test so the detectors are not only in the upstairs living room by default. This page does not price tanking, a sump or a fan. Those are different trades and different questions.
What should you ask your surveyor?
- Did you enter the cellar, and is any of it used as a room?
- Are you relying on a map that UKradon says not to use for cellars?
- Is there already a sump, and is there a test?
What are the typical next steps?
- Do not clear the radon question from the map colour if there is a cellar.
- Commission a measurement if the cellar is part of how you will live.
- Read the damp and timber lines for the cellar as their own findings.
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 a coal cellar under the pavement the same as a basement room?
It is still an underground space. Do not assume the map ignored it. Ask whoever scopes the test what they can actually measure.
Does a dry cellar mean low radon?
No. Damp and radon are different. Dry tells you about water you can see.