Asbestos cement is a mix of cement and asbestos fibre that was made into hard flat boards, corrugated roofing sheets, pipes and ducts. The grey board, often called "mineriitti" in everyday Finnish, was used on roofs and façades, in wet rooms and in technical spaces, and a board installed before 1994 may contain asbestos. Modern fibre-cement boards are asbestos-free and look almost identical, so neither the look nor the age of a board settles the question. Only a sample analysed in a laboratory gives you certainty.
This article covers where asbestos cement is typically found, why a board cannot be identified by eye, what you should not do to it, how to take a sample and what the result means. Finally, it explains how asbestos cement boards are disposed of.
What is asbestos cement?
In asbestos cement, the asbestos fibres act as reinforcement inside the cement and make a thin board strong. The material is hard, dense and weather-resistant, which is why it was used both outdoors and indoors. In an intact board the fibres are bound by the cement. Fibres can be released when the board is sawn, drilled, sanded or broken, or when its surface has weathered over decades.
Where was asbestos cement used?
Roofs and corrugated sheets
Flat and corrugated asbestos cement sheets were used on the roofs of houses, saunas, garages, sheds and farm buildings. Roof sheets are often the ones that have been exposed to the weather the longest. If the roof has roofing felt, that is a separate material, covered in the article asbestos in roofing felt.
Façades, plinths and eaves
Façade boards, plinth protection boards, soffit boards under the eaves and balcony panels are typical uses of asbestos cement. The boards are often painted, so the original surface cannot be seen at all.
Wet rooms and technical spaces
An asbestos board in a wall is possible, for example, under the tiles in a bathroom, behind a sauna stove, in a heat distribution room or in a boiler room. The board may be covered with filler, paint or tiles, which are layers of their own. The layers of a wall are covered in more detail in the article asbestos in walls.
Pipes and ducts
Asbestos cement was also used for water and sewer pipes, downpipes, and ventilation and flue ducts. They can be found underground, inside structures and on the roof.
Fire protection
Boards were used as fire protection around fireplaces, sauna stoves and heating boilers, and in fire compartment walls. In such places the board is often small and easy to overlook.
Why do looks and age decide nothing?
In modern fibre-cement boards, asbestos has been replaced by other fibres, but the boards are still grey, hard and the same size as the old ones. New boards may have been fitted among old ones in an older building, and paint hides the difference even further. Markings on the back of a board are often missing or illegible. The year of construction is not enough either: the boards on a 1970s house may have been replaced later, and a neat-looking board can still be decades old. That is why the decision is made on the basis of a sample.
What should you not do to an asbestos cement board?
- Do not saw, drill or sand the board, and do not cut it with an angle grinder.
- Do not break the board or drop it if you have to move it.
- Do not pressure-wash roof or façade boards, and do not scrub moss off with a stiff brush. Washing loosens the weathered surface and spreads it around.
- Do not walk on old corrugated roof sheets. A weathered sheet can also give way.
An intact but weathered board is no reason to panic, but it is a reason for care. When the surface has become brittle, the fibres are closer to the surface and come loose more easily. Leave the board alone until you know what it contains, and plan the repair accordingly.
When should a board be tested?
A board should be tested before anything is done that breaks it: replacing the roof, renovating the façade, painting that requires washing or sanding, drilling for new fixings, stripping out a wet room or demolishing an outbuilding. The result also tells you whether the removed board is handled as asbestos waste or as ordinary construction waste.
How do you take a sample from an asbestos cement board?
If there are boards in different places or boards installed at different times, for example on the roof and on the façade, or in a repaired spot, take a separate sample from each. A good rule of thumb is one sample per different board.
- Choose a spot at the edge or corner of the board, preferably one that is already chipped or out of sight.
- Wear disposable gloves and a respirator of at least class FFP3.
- Lightly mist the spot with a spray bottle to keep dust to a minimum.
- Using pliers, snap off a small piece of a few centimetres from the edge or corner. Do not saw or drill. If the board is painted, take the piece with the paint on.
- Drop the piece straight into a zip-lock bag, seal it and put it inside a second bag.
- Mark the bag with the sample location, for example "garage, corrugated roof sheet, north edge".
- Cover the broken spot with tape and wipe the area with a damp cloth.
More guidance is available in the articles how to take an asbestos sample and protecting yourself when sampling asbestos.
What does the result mean?
Onelab analyses the sample with a JEOL SEM-EDS electron microscope in accordance with ISO 22262-1, and the result is sent by email, typically on the day the sample arrives. The result tells you whether asbestos was detected in the sample you sent.
- No asbestos detected: no asbestos was detected in the board, and a removed board is handled as ordinary construction waste according to your local instructions. The result applies to the tested board and similar boards. Boards installed at other times are tested separately.
- Asbestos detected: removing, cutting and drilling the board are planned as asbestos work. Where required, the removal is carried out by a company authorised for asbestos removal work. An intact board can also stay in place as long as it is not broken or washed.
If the boards are part of a larger renovation or demolition that requires an on-site asbestos survey, the survey is carried out on site by a qualified surveyor. Onelab is a laboratory, and on-site surveys are handled by our sister brand AsbestiPro.
Disposing of asbestos cement boards
An asbestos-containing board is removed as intact as possible, moistened and packed tightly in double, thick plastic with the seams taped. The packages are marked as asbestos waste and taken to a waste centre or other reception point that accepts asbestos. Check with your local waste management company which reception point to use, whether you need to book in advance and how the waste must be packed. When a contractor carries out the removal, they usually also take care of packing and delivering the waste. Read more in the article disposing of asbestos waste.
In old detached houses, asbestos cement is often just one material among many. The article asbestos in a Finnish post-war house goes through the other renovation layers in an old house that are worth sampling.
How much does the analysis of an asbestos cement board cost?
The analysis costs €39.90 + VAT per sample, and the price is the same for 1–100 samples. Orders of more than 100 samples can be priced separately. Postage is not included. You can order the analysis online and send the sample to the laboratory by post.