Radon in a rental dwelling in Belgium: risks and obligations
Radon in a rental dwelling in Belgium. Health risks, risk zones, landlord's obligations, measurement, and remediation works.
Health risks of radon
Radon is a natural radioactive gas, odourless and colourless, that infiltrates buildings through the ground. It is the second leading cause of lung cancer after smoking.
Radon in figures
| Data | Value |
|---|---|
| Reference threshold (Europe) | 300 Bq/m3 |
| Recommended threshold (FANC Belgium) | 100 Bq/m3 |
| Belgian dwellings > 300 Bq/m3 | Approximately 3% |
| Belgian dwellings > 600 Bq/m3 | Approximately 0.5% |
| Radon-related lung cancer deaths (Belgium) | Approximately 480/year |
| The landlord has a general obligation to deliver a dwelling that does not endanger the tenant’s health. A high radon level may constitute a habitability defect. |
Risk zones in Belgium
Mapping
Radon is primarily present in regions with a shale or granite subsoil:
| Zone | Risk | Provinces |
|---|---|---|
| Ardennes | High | Luxembourg, Namur (south), Liege (south) |
| Entre-Sambre-et-Meuse | Medium to high | Namur, Hainaut (east) |
| Walloon Brabant | Low to medium | Walloon Brabant |
| Brussels | Low | Brussels-Capital |
| Flanders | Very low | All provinces |
Aggravating factors
Certain buildings are more exposed: construction in direct contact with the soil (basements, cellars), cracks in the slab or foundations, absence of crawl space ventilation, porous building materials. For other health risks, see our guide on asbestos in a rental.
Measuring radon
How to measure
Radon measurement is done with a passive detector placed in the dwelling for a minimum of 3 months (ideally in winter).
| Method | Cost | Duration | Precision |
|---|---|---|---|
| Passive detector (FANC) | 20-30 EUR | 3 months | High |
| Electronic detector | 150-500 EUR | Instant | Medium |
| Professional measurement | 200-500 EUR | 1-3 months | High |
Interpreting results
- < 100 Bq/m3: no action necessary
- 100-300 Bq/m3: improvements recommended (ventilation)
- 300-600 Bq/m3: remediation works recommended
- > 600 Bq/m3: urgent remediation works The FANC (Federal Agency for Nuclear Control) offers detectors at reduced prices via its website.
Remediation and landlord’s obligations
Remediation works
| Intervention | Indicative cost | Effectiveness |
|---|---|---|
| Crawl space ventilation | 500 - 2,000 EUR | Good |
| Crack sealing | 200 - 1,000 EUR | Medium |
| Sub-slab depressurisation system | 1,500 - 4,000 EUR | Excellent |
| Mechanical ventilation (MVHR) | 3,000 - 6,000 EUR | Good |
Landlord’s obligations
The landlord must: deliver a habitable dwelling (general obligation), inform the tenant if a high level is known, bear the remediation works costs (major repair), allow radon measurement by the tenant.
Tenant’s remedies
If the landlord refuses to act in the face of a high radon level:
- Formal notice by registered letter
- Report to the regional housing service
- Referral to the justice of the peace For the landlord’s general obligations, see our guide on the landlord’s obligations and works in a rental.
Frequently asked questions
-
No, a radon assessment is not mandatory in Belgium for letting. However, it is strongly recommended in risk zones (Ardennes, southern Belgium).
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The European reference threshold is 300 Bq/m3. FANC recommends action from 100 Bq/m3. Above 600 Bq/m3, remediation works are strongly recommended.
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The landlord bears the cost of remediation works (ventilation, crack sealing, depressurisation system). These are major repairs related to the building's structure.