Asbestos Diagnosis Thônex

Thônex: a residential fabric marked by the at-risk decades

Thônex is one of the residential municipalities of the eastern ring of Geneva. Bordering the French frontier, it developed primarily between the 1950s and the 1980s, during the period of maximum asbestos use in Swiss construction. This concentrated urban development timeline places a significant proportion of Thônex’s building stock in the asbestos risk zone.

The Thônex built fabric is dominated by individual villas and small three-to-five-storey buildings constructed between 1960 and 1980. These residential buildings share the characteristic of having been built to the construction standards of the time, which systematically integrated asbestos-based materials: fibre cement on roofs and cladding, vinyl tiles in interiors, thermal and acoustic insulation on pipes.

The Mon-Idée district, a characteristic sector of Thônex, well illustrates this density of villas and small buildings from the 1960s–1970s. The quiet, leafy streets of this residential district concentrate a building stock that, for a significant proportion, dates from the critical period. Garden annexes, garages and shelters built at the same time often present fibre cement roofs or cladding.

The proximity with Chêne-Bougeries and Chêne-Bourg also defines part of the Thônex built fabric: medium-scale buildings constructed on the edge of villa zones, responding to the same logic of residential development from the 1960s–1980s.

Which buildings are concerned in Thônex?

Thônex’s built profile concentrates on two main typologies, with asbestos-containing materials typical of residential construction of the period.

Villas and single-family houses

Villas constructed between 1960 and 1980 form the core of the asbestos issue in Thônex. The materials concerned are characteristic of individual residential construction of the period: corrugated or flat fibre cement sheet roofs and cladding, vinyl tiles in living spaces and cellars, tile adhesives in bathrooms and kitchens, thermal insulation on hot water pipes.

Annexes and garages constructed at the same time frequently present fibre cement roofs, sometimes in apparently good condition but whose composition must be verified before any intervention. Successive extensions built on these villas constitute additional layers to be analysed during the diagnosis.

Small collective buildings

Small residential buildings of three to five storeys constructed in the 1960s–1980s present configurations closer to the large Genevan developments: vinyl tiles in common areas and apartments, asbestos-cement ventilation ducts, fibre cement on spandrel panels and balcony cladding, heating column lagging. Boiler rooms in these small collective buildings often concentrate degraded lagging materials.

Business buildings and municipal facilities

A few craft business buildings and municipal facilities constructed in the 1960s–1970s complete the picture. These constructions often present large-span fibre cement roofs and lightweight interior partitions based on asbestos-cement.

Common asbestos-containing materials in Thônex

Thônex’s built fabric from the 1960–1980 period presents materials characteristic of residential construction of the period:

• Corrugated or flat fibre cement sheets on roofs, cladding and facade cladding
• Vinyl-asbestos floor tiles in living spaces, cellars and garages
• Adhesives for laying vinyl tiles and ceramic coverings (black or brown adhesives)
• Thermal insulation on heating and domestic hot water pipes
• Asbestos-cement ventilation ducts in kitchens and bathrooms
• Roof underlay and lining panels in chalet-type constructions
• Joints and mastics around joinery and pipe penetrations
• Interior finishing renders applied in the 1960s–1975 period

Cellars and technical rooms in villas and small collective buildings are the most frequent concentration zones for degraded materials.

Regulations applicable in Thônex

Thônex is located in the canton of Geneva, subject to one of the most demanding regulations in Switzerland regarding asbestos. The prior investigation obligation applies to any construction site likely to disturb materials in a building predating 1991, including for minor works that do not require a building permit.

For projects subject to building permit, the diagnostic report must be attached to the file submitted to the Building Permits Office (OAC) of the canton of Geneva. The report must be prepared by a FACH-recognised expert. For villas, the diagnosis scope includes the entire main building and any annexes concerned by the works.

The federal Ordinance on Construction Work (OTConst) further requires every contractor to be informed of the presence of asbestos before intervening on a building predating 1991. This obligation applies even for routine works such as roof replacement or bathroom renovation.

Neighbouring communes served

We operate in Thônex and all neighbouring communes:

• Geneva city (Eaux-Vives, Champel)
• Chêne-Bougeries
• Carouge
• Chêne-Bourg
• Vandoeuvres
• Choulex

Frequently asked questions about asbestos diagnosis in Thônex

My villa in Thônex dates from 1968 and has never been renovated. Does it contain asbestos?

A 1968 building was very probably constructed with asbestos-containing materials, particularly on the roof, cladding and floor coverings. The absence of renovation does not mean the absence of risk: original materials may be asbestos-containing. Only a diagnosis with laboratory analyses can confirm the presence and precisely locate the materials concerned.

The fibre cement roof of my villa is in good condition. Do I still need a diagnosis before replacing it?

Yes, without exception. The apparent condition of a material does not prejudge its composition. Many fibre cement sheets in good visual condition contain asbestos. Before any replacement or removal, a diagnosis with laboratory analysis is mandatory. If the presence of asbestos is confirmed, specialist companies must intervene for the removal.

My contractor for cellar works is asking for an asbestos diagnosis. Is this justified?

Entirely. The OTConst requires the contractor to be informed of the presence of asbestos before intervening on a building predating 1991. For a cellar constructed in the 1960s–1980s, floor tiles, pipe insulation and renders are common at-risk zones. This request from the contractor is legally founded and professional.

Can the diagnosis and the decontamination works be carried out by the same company?

No, it is strongly inadvisable to entrust the diagnosis and the decontamination to the same entity. The diagnostician must be independent of the decontamination company to guarantee the objectivity of their report. However, the diagnostician can direct you towards specialist companies after delivering their report.

How many samples are needed for a standard-sized villa in Thônex?

The number of samples depends on the number of suspect materials identified during the visual inspection. For a standard villa from the 1960s–1980s, generally allow between 5 and 15 samples depending on the materials in place and the zones to be investigated. The expert assesses the scope during the visit and adapts the number of samples to the actual situation of the building.