DIY GUIDE · TRADES & CONSTRUCTION · CHECKED OCTOBER 2026
How to test your home for radon yourself
Ten minutes of work and three months of waiting. £52.80 for a validated test pack, or £56.70 with an address check first.
Two detectors, two rooms, three months, posted back — then act on the number.
- Every step, start to finish
- Checked October 2026 — sources at the end
- Honest about when to call a pro
FIRST, THE HONEST ANSWER
Do it yourself, or get a builder?
Do it yourself if…
- You want to know the radon level in a home you own or rent and live in
- You can leave two detectors in place for three months while the home is lived in normally
- There will be no building work, no long absence and no change of occupier during the test
- You are happy to post the detectors back on the date given
Get a pro if…
- The result is at or above the Action Level and you need radon reduction designed and installed
- You are buying or selling and need a measurement on a deadline shorter than three months
- It is a workplace or a rented property you manage, where the duties are an employer's or landlord's
- The home has an occupied basement or an unusual construction and you want a survey of where the gas gets in
Safety first
- The detectors themselves are safe: the measurement service says they emit nothing and collect nothing dangerous. Do not open them, heat them or get them wet, or the result is lost.
- Radon is a long-term risk, not an emergency. A high result means acting within months, not leaving the house tonight — but it does mean acting, because the risk builds with years of exposure.
- Smoking multiplies the lung cancer risk from radon. If anyone in the home smokes, a high result matters even more.
- Do not try to dig a sump or cut into a solid floor yourself. Breaking up floors can disturb services, damp-proofing and, in a home built before 2000, materials containing asbestos.
- If you fit a fan or ventilation to reduce radon, it is wired electrical equipment: the electrical connection is a job for a registered electrician.
Stop here: Stop here: reducing the radon
Placing the two detectors and posting them back is yours to do. Reducing radon is not, and the danger of a half-done job is real: HSE describes radon as the second largest cause of lung cancer. At or above the Action Level of 200 Bq m-3 the fix is a radon sump or under-floor ventilation, which means cutting into the floor or the ground beneath the house and usually a fan that runs all the time. UKHSA’s guidance says sealing gaps alone is not enough, so the system should be designed and fitted by a radon remediation specialist, and a fan wired into the mains is a job for an electrician. How to hire a radon specialist →
| MATERIAL | COVERAGE | FOR THIS JOB |
|---|---|---|
| Radon detectors | Two per home: living area and bedroom | Two |
| Pre-paid return envelope | Supplied with the pack | One |
| Address risk report | Optional, before testing | One |
How your result is worked out
Estimated yearly average = (0.42 × living-area reading + 0.58 × bedroom reading) × the seasonal correction for the months measured. The validation scheme's own example: a weighted reading of 46 Bq m-3 with a seasonal factor of 1.37 gives 46 × 1.37 = 63 Bq m-3.
The laboratory does this for you; it is here so you can see why both rooms and the right dates matter.
The measurement service sells an address search report for £3.90 showing whether the address falls in a radon Affected Area, and advises measuring where it does. Many people simply test, because levels vary from house to house even next door, and the safety regulator notes that results from a neighbouring building cannot stand in for yours.
Measurements that can be compared with the Action Level come from laboratories validated under the national scheme run by UK Health Security Agency. Its own home pack is validated, costs £52.80 including VAT and includes two detectors, placement instructions and a pre-paid envelope. Other validated laboratories exist; whichever you choose, check it is on the validated list.
Radon levels swing from day to day and season to season, so the validation scheme only covers measurements of 3 months or longer. Short tests of a few days can be useful for a rough screen, but they give a much less reliable estimate of the yearly average, and the yearly average is what the Action Level is set against.
A home test uses two detectors placed at the same time: one in the main living area and the other in a bedroom that someone sleeps in. Measuring both together cancels out short-term swings, and they are the rooms where you spend the most time, which is what the dose is about.
Any time of year works, because the laboratory applies a seasonal correction to turn a three-month result into an annual estimate. What matters more is that the home is lived in normally for the whole period.
THE PART THAT DECIDES THE FINISH
Before you start — by the kind of home you have
Radon comes up from the ground, so where it collects depends on how your home meets the ground. Find your home below and check its list before you place the detectors.
A house with a solid concrete ground floor
The commonest case, and the one where a sump usually works best if the level is high.
- Place the living-area detector in the main ground-floor living room
- Place the bedroom detector in the bedroom used most, whichever floor it is on
- Note any large cracks, gaps around pipes or open service entries in the floor for later — but do not seal them during the test
A house with suspended timber floors
Air moves under the floor through airbricks.
- Check the airbricks round the outside walls are not blocked by soil, plants or paving, and note any that are
- Do not clear or block airbricks during the test; measure the house as it normally is
- Place the detectors in the living room and an occupied bedroom as normal
A flat on the first floor or above
Usually lower levels, but not always zero.
- Check whether your area is an Affected Area before paying for a test
- If you test, use the living area and the bedroom as usual
- A ground-floor or basement flat should be tested like a house
A home with an occupied basement or cellar
The highest-risk rooms are below ground.
- The measurement service says any basement occupied for more than 50 hours a year should be monitored regardless of the area's radon potential
- Treat an occupied basement room as the living area or bedroom it is used as
- Tell the laboratory which floor each detector was on, because it affects the calculation
A new build or a recent extension
Radon protection may be built in; test anyway.
- In areas of higher radon potential new homes may have a membrane or a sump built in, but the safety regulator notes even protected buildings can have high levels
- Wait until the home is lived in normally before testing
- Test after any major work to the ground floor, because it changes how the gas gets in
THE JOB
How to test your home for radon
Decide whether and when to test
15 minLook up whether the address falls in a radon Affected Area, or decide to test anyway. Then look at the next three months: you need the home lived in normally throughout, with no building work, no absence longer than a short holiday, and no change of who lives there. Go to the section above for your type of home and note which rooms you will use.
- An address report costs a few pounds and is optional
- Avoid the months of a planned extension, new windows or a long trip
- Choose the bedroom that is slept in every night
Mistake to avoid: Ordering the pack and then going away for a month. The measurement service rules a test out if the home stands empty for longer than 2–3 weeks during it.
Order a validated pack for your address
10 minOrder a home measurement pack from a laboratory validated under the national scheme, for the exact address you will test. The measurement service's own pack comes with two detectors, placement instructions and a pre-paid envelope, and may take 7–10 working days to dispatch.
- Detectors can only be used at the address they were ordered for
- Check the laboratory is on the validated list if it is not the national service
- Put the expected arrival in your diary so you can place them promptly
Mistake to avoid: Leaving the pack in a drawer for weeks. The detectors record continuously from the moment they arrive, and the service says they must be placed within a few days.
Read the placement instructions and the detector labels
5 minEach detector is labelled for its room. Read the position marked on the flat side of each one so the living-area detector goes in the living area and the bedroom detector in the bedroom. Mixing them up makes the calculation wrong, because the two rooms are weighted differently.
- Living-area detector in the main living room
- Bedroom detector in an occupied bedroom
- Keep the instruction sheet with the placement form
Mistake to avoid: Swapping the detectors between rooms. The laboratory weights the bedroom more heavily, so a swapped pair gives a wrong yearly average.
Place the detectors properly
10 minPut each detector at about breathing height — the validation scheme says 1 to 2 metres off the floor — on a shelf, a bedside table or a noticeboard, or hang it from its loop. It can sit any way up. Keep it off the floor, away from draughts at window sills and mantelpieces, away from radiators, hot pipes, electrical equipment and direct sun, out of cupboards and drawers, and away from sinks.
- A bookshelf or bedside table is ideal
- Somewhere it will not be moved, cleaned round or knocked off
- Out of reach of children and pets who might chew or open it
Mistake to avoid: Putting a detector on the window sill or on top of a radiator. Draughts and heat both distort the reading, and heat can damage the detector.
Record the start date
2 minWrite the date you placed each detector on the placement sheet, along with the room and the floor it is on. Set a reminder for the removal date.
- Same date for both detectors; they must run at the same time
- Note the floor level of each room
- Photograph the completed sheet in case it is lost
Mistake to avoid: Not recording the dates. The seasonal correction depends on exactly which months were measured.
Live normally for three months
3 monthsLeave the detectors where they are and use the home as you always do — heating, windows and doors as normal. Do not move the detectors, open them, or change the house in ways that affect air movement, such as blocking airbricks or starting building work.
- Normal life is the point; do not air the house more than usual
- If a detector is knocked down, put it straight back in the same place
- Tell the laboratory if anything unusual happened during the test
Mistake to avoid: Opening every window to be safe while the test runs. It lowers the reading for those months, so the result understates what you normally breathe.
Return the detectors
10 minOn the removal date, collect both detectors, write the removal date on the placement sheet, and post them back together in the pre-paid envelope with the form. The measurement service says results are posted around 4 weeks after it receives the detectors.
- Return both together; one detector alone cannot be weighted properly
- Post them promptly after removal
- Keep a copy of the dates you wrote
Mistake to avoid: Keeping the detectors for an extra month and posting them late. The extra time is not on the record, and the result may not be valid.
Read the result
15 minThe report gives an estimated yearly average for the home, worked out from both detectors and corrected for season. Compare it with the figures in the validation scheme's advice: below 100 Bq m-3 no remedial work is needed; between 100 and 200 Bq m-3 consider reduction measures; at or above the Action Level of 200 Bq m-3 install remedial measures and retest.
- The yearly average is the number that matters, not either room on its own
- Keep the report with the house papers
- If you smoke, a result in the middle band matters more
Mistake to avoid: Reading the bedroom figure alone and panicking, or the living room alone and relaxing. The estimate combines both, weighted and corrected.
Do the simple things if the level is raised
1 hourCheck airbricks are clear on a suspended floor, and that large openings in the ground floor, such as gaps round service pipes, are sealed. The measurement service is clear that sealing gaps and adding ventilation will not bring radon down by themselves; they help when combined with an effective measure such as a sump or under-floor ventilation, so treat them as preparation rather than a cure.
- Clear blocked airbricks of soil and plants
- Seal large gaps round pipes entering through the floor
- Your council's environmental health team may be able to advise
Mistake to avoid: Sealing a few cracks and assuming the problem is solved. Complete sealing of a floor is very difficult, and partial sealing alone rarely brings a high level down.
Get remediation designed, then retest
3 monthsFor a result at or above the Action Level, get a radon remediation contractor to recommend and install the right measure for your floor type — the measurement service lists a radon sump as the most effective for solid floors, and under-floor ventilation for suspended ones. After the work, measure again for three months to check it worked; the service says a free retest is sometimes available after remediation.
- Ask the contractor what level they expect to reach and how they will prove it
- Keep the sump fan running; switching it off brings the radon back
- Retest after any later building work to the ground floor
Mistake to avoid: Paying for remediation and never measuring again. Only a retest shows the level has actually come down.
The mistakes that spoil the result
- Placing a detector on a window sill, a radiator or in a cupboard
- Leaving the house empty for weeks, or doing building work, during the test
- Swapping the bedroom and living-area detectors
- Using a short test and treating it as the yearly average
- Sealing a few cracks and not retesting
Stop here and get a radon remediation specialist
- The result is at or above the Action Level of 200 Bq m-3 — a sump or ventilation system needs designing for your floor
- Reduction work would mean cutting into a solid floor, digging under the house or fitting a fan that needs wiring
- The home has an occupied basement or cellar with a high result
- You have tried simple measures and a retest is still high
| WHAT YOU SEE | WHY, AND THE FIX |
|---|---|
| My result says the test was invalid | Usually building work, a long absence, a change of occupier, or detectors placed or returned outside the rules. Order a new pack and test again for three months while the home is in normal use. |
| The two rooms gave very different readings | That is common: radon varies from room to room and floor to floor. The estimate combines both; if the result is high, the floor with the higher room is where remediation will focus. |
| My neighbour's result was low, so mine must be | Not necessarily. The safety regulator notes levels in neighbouring and even adjoining buildings can differ greatly, so a neighbour's result cannot be used for your home. |
| A short-term monitor says my level is high | A test of days is only a screen. Radon swings day to day, so confirm with a validated three-month test before deciding on remediation. |
| I lost one of the detectors | Contact the laboratory. One detector on its own cannot be weighted the same way, so you may need a new pack. |
| The result is between 100 and 200 | Below the Action Level but in the band where the validation scheme's advice is to consider reduction measures, especially if anyone smokes. Simple measures plus a retest are a sensible start. |
| The level is still high after remediation | The system may need adjusting, extending or a stronger fan, or there is another entry route. Ask the contractor to check it and measure again. |
WHAT YOU SAVE
What it costs to do it yourself
| Address risk report, optional | £0–£3.90 |
|---|---|
| Validated two-detector home measurement pack | £52.80 |
| Total | £52.80–£56.70 |
| DIY total | £52.80–£56.70 |
Guide prices compiled by the Locufy team from published Irish and UK provider price lists and 2026/27 cost guides. Updated 2026.
Testing is cheap; remediation is where the cost lies. The price guide's band covers both testing and mitigation work, so its higher figures reflect installing a sump or ventilation rather than the test itself.
RATHER NOT?
Radon specialists near you, with prices shown
The ones who cover your area, nearest first, with one score from every review. No account needed to look.
Or post the job free and let them come to you.
Buyers and their solicitors may ask about radon in an Affected Area. A validated result, and a retest after any remediation, answers the question.
Measure again after remediation, after major work to the ground floor such as an extension or new floor, and from time to time if the level was close to the Action Level.
The test detectors go back to the laboratory, so nothing is left to throw away but the packaging, which goes in your household recycling. An electronic radon monitor is electrical waste: take it to your council's household waste and recycling centre with small appliances, or back to a retailer that offers take-back when you buy a new one.
A sump works only while its fan runs. Check it is on, listen for changes in the fan, and have it serviced as the installer recommends.
Testing your home for radon: questions people ask
Order a validated home measurement pack, put one detector where you sit in the evenings and one in a bedroom that is slept in, both at breathing height for three months, then post them back. The measurement service's own pack costs £52.80 and includes two detectors and a pre-paid envelope.
The detectors stay in place for 3 months, the validated minimum. The measurement service says results are posted around 4 weeks after the detectors reach it.
The UK Action Level for homes is 200 Bq m-3 as a yearly average. The validation scheme's advice is that below 100 no remedial work is needed, from 100 to 200 reduction measures should be considered, and at or above 200 they should be installed and the home retested.
As a guide, yes, but only measurements of 3 months or longer are covered by the national validation scheme, because radon changes from day to day. Confirm any worrying reading with a validated three-month test.
Simple steps such as clearing airbricks and sealing large gaps help only when combined with an effective measure. A sump or under-floor ventilation system needs designing and installing by a specialist, and any fan wiring by an electrician.
The Locufy UK price guide puts radon testing and mitigation at £40–£2,000 per job, typically £800 — the same three figures as the strip at the top of this page. The low end is a test; the high end is remediation work.
MORE GUIDES
More DIY guides
Sources — checked October 2026
- HSE — radon in the workplace: passive detectors by post, second largest cause of lung cancer, neighbouring results not usable, sumps
- UKradon (UKHSA measurement service) — order a home measurement pack: £52.80, two detectors, 7–10 working days, 3 months, results about 4 weeks after return, invalid if empty for 2–3 weeks
- UKradon (UKHSA measurement service) — measuring radon: risk report £3.90, basements used more than 50 hours a year, Action Level 200 Bq m-3
- UKradon (UKHSA measurement service) — how to reduce radon levels: sumps, under-floor ventilation, sealing alone not enough
- UKHSA on gov.uk — validation scheme for radon measurements in UK buildings (2018): 3 to 12 months, two detectors, 1 to 2 metres, 0.42 and 0.58 weights, advice bands 100 and 200 Bq m-3
- UKHSA on gov.uk — radon collection: what radon is and the health risk
- gov.uk — electrical waste: retailer take-back
- North Northamptonshire Council — what can be recycled at household waste recycling centres (small appliances)