When you enter the roof truss of an old building and it smells musty and chemical, this may be caused by old wood preservatives. PCP (pentachlorophenol) and lindane (γ-hexachlorocyclohexane) were extensively incorporated from the 1960s through the 1990s into products such as Xylamon, Xyladecor, and Basilit — PCP against fungi, lindane against insects. Often in combination.
The problem: both substances continue to off-gas even 30–40 years after application. And both are toxic.
Where We Find Old Wood Preservatives
In the buildings we inspect — primarily built between 1960 and 1990 — we typically find treated timber at these locations:
- Roof trusses: The classic find location. Rafters, purlins, collar beams — painted over broad areas or dip-treated.
- Timber framing and timber beam ceilings: In old buildings with exposed timber.
- Basement beams: Timber exposed to moisture was treated particularly intensively.
- Timber cladding and panelling: Wall panelling, ceiling panels.
Recognisable by brownish, greenish, or oily discolouration of the wood. Sometimes you can also smell it — a sweet-chemical odour, especially on warm days or in poorly ventilated rooms.
Why PCP and Lindane Are Problematic
PCP: Liver damage, immunosuppression, skin diseases (chloracne). IARC classifies PCP as "possibly carcinogenic" (Group 2B). Particularly insidious: technical-grade PCP contains dioxins and furans as impurities — highly toxic substances that accumulate in the body. PCP has been banned in Austria since 1990.
Lindane: Neurotoxin, liver damage, endocrine disruption. IARC has classified lindane as a Group 1 carcinogen since 2015 — definitively carcinogenic. The EU-wide ban as a persistent organic pollutant (POP) came in 2004.
Both substances accumulate in household dust. In attic apartments with treated rafters, we regularly measure relevant concentrations in the indoor air — even decades after application.
German guideline values serve as reference: PCP 0.1 µg/m³ (precautionary), 1 µg/m³ (action threshold). Lindane 0.5 µg/m³ in indoor air.
How We Detect Wood Preservatives
We take wood shavings or a dust sample. The laboratory analyses by GC-MS for PCP, lindane, and related substances.
A material analysis costs from €85. For suspected indoor air exposure — especially with a roof conversion or a converted attic — we recommend an indoor air measurement (from €250).
→ More about wood preservative testing
What You Can Do
Treated timber in closed, unventilated rooms: No use as a living space until a measurement has been taken.
Roof conversion planned: Measure before conversion, without exception. Remediation costs for PCP-contaminated timber are substantial — sealing (70–90% reduction) or timber replacement.
Contamination confirmed, residential use: Sealing of timber surfaces, intensive ventilation, regular monitoring. In severe cases: timber replacement.
Wood preservatives are one of the pollutants routinely checked during a pollutant check before a home purchase (→ Pollutant check) — especially if the roof truss is converted or is to be converted.
When You Should Get in Touch
You are planning a roof conversion in a building from before 1990? You can smell chemicals in the attic? You live under treated rafters and have questions?
15-minute initial consultation, free of charge.