How many asbestos samples do you need to take?

You take one asbestos sample from each distinct material or layer build-up that the renovation will demolish, sand or drill into. The number of samples does not depend on the number of rooms or square metres, but on how many different materials, layer build-ups and repairs from different periods there are in the work area. Renovating a single wall or floor often needs just one sample, while stripping out a whole home typically needs several.

This article shows how to work out the number of samples, when one sample covers a large area and when even identical-looking materials need separate samples.

The basic rule: one sample per material

The laboratory analyses what is in the bag. The result applies to the sampling spot and to similar material, meaning the same product installed at the same time. So the number of samples depends on how many different materials there are in the work area. A material counts as a separate case when it is:

• A different material: vinyl flooring, tile adhesive, wall filler, pipe insulation and fibre cement board each need their own sample, even in the same room.
• A different layer build-up: tiles set in mortar and tiles fixed with adhesive over filler are different build-ups.
• A different installation: original material and material added in a later renovation are different products, even if they look the same. Patched areas are also often a different material from their surroundings.
• In a different part of the building: even identical-looking material is tested separately if it is, for example, in a wet room and in a dry room.

Floor area alone does not add samples: if two bedrooms have the same vinyl flooring laid at the same time, one sample represents both. The layers of one build-up, such as tile, mortar and adhesive, are sent as a single sample so that no layer goes untested.

How to work out the number of samples, step by step

1. List the jobs. Write down what you plan to demolish, sand, chisel or drill. Painting an intact surface without sanding or scraping does not break the old layers.
2. Check what each job breaks. A damaged spot or the space behind a skirting board often shows the layer build-up.
3. Group what is alike. Combine spots where the material looks the same, is installed the same way and probably dates from the same renovation.
4. Separate what differs. Patches, a different colour or pattern, a different substrate, a different part of the building and a different renovation are all reasons for a separate sample.
5. Take one sample from each group. Number the bags and note which area each sample represents, for example "S1 kitchen, floor, vinyl and adhesive". Use the same names in your order so that each result is matched to the right spot.
6. If in doubt, take an extra sample. Testing both materials is cheaper than stopping the demolition later.

When is one sample enough for a large area?

When the material is uniform: the same appearance, the same substrate and the same installation date throughout. Examples are the floor covering of one room, the tiling of one wall or a uniform ceiling filler. Take the sample from a spot that is typical of the whole area, not from a repaired corner, for example. If you only need to drill fixings into a tiled wall, one sample of that wall's layer build-up is enough.

When do identical-looking materials need several samples?

• The building has been renovated in stages. The vinyl in the hall and in the kitchen may look the same yet come from different decades.
• The surface has patches. A patched spot is often made with a different filler or adhesive.
• An old surface lies under a new one. Hidden old flooring or tiles belong in the sample. If the layers are removed separately, they can be sampled separately.
• Different flats are involved. In a block of flats, each home may have been refurbished at a different time, so the result from one flat cannot simply be applied to the neighbours. Read more in the article asbestos in blocks of flats.

Examples of the counting method

The sample numbers below illustrate the method and are not norms: the right number depends on what your particular renovation will break.

• Bathroom: if the walls have one tiling and the floor another, this example needs two samples, each with all its layers. Ceiling filler that will be sanded is a third sample, and partly replaced tiling is tested separately. See also asbestos in the bathroom.
• Kitchen: the vinyl floor with its adhesive, the splashback tiling between the cabinets and a wall that will be opened make three samples in this example. If the same floor, laid at the same time, continues into the hall, one floor sample covers both.
• Floors throughout the home: the same flooring laid at the same time in every room can mean one sample. If the hall has a different floor, the kitchen has vinyl tiles and the bedrooms have vinyl sheet flooring, that makes three samples.
• Major renovation of a detached house: an older house may have materials from many decades, such as pipe insulation in the basement, boards on the facade or roof, and fillers and floors indoors. The sample count follows from the list of materials, so it can reach ten or more. See also asbestos in post-war veterans' houses. A large strip-out may need an asbestos survey. Onelab is a laboratory, and on-site surveys are handled by our sister brand AsbestiPro.

Do not mix different materials in one bag

If pieces of floor covering, wall filler and tile adhesive are in the same bag, a positive result does not tell you which of them contains asbestos, and all of them have to be treated as asbestos-containing. The sampling guidance of the Finnish Institute of Occupational Health also says a sample should represent only one material. So pack each material in its own bag and keep the layers of one build-up together.

Sampling in brief

1. Wear disposable gloves and a respirator of at least class FFP3.
2. Mist the sampling spot with a spray bottle.
3. Remove a piece of about 2–5 centimetres through all layers down to the substrate.
4. Put the piece in a zip-lock bag and that bag inside a second bag.
5. Mark the bag with the sample number and location.
6. Cover the spot with tape and wipe the area with a damp cloth.

More detailed instructions are in the article how to take an asbestos sample.

What does the result tell you when there are several samples?

Onelab analyses each sample separately with a JEOL SEM-EDS electron microscope, and the report gives a result for each sample. It arrives by email, typically on the day the samples arrive. Each result applies to the group of material that the sample represents, so clear numbering matters as much as the sample itself. If asbestos is detected in any sample, read on in the article positive asbestos result.

How much does analysing several samples cost?

The analysis costs €39.90 + VAT per sample, and the price is the same for 1–100 samples. Three samples therefore cost 3 × €39.90 + VAT. Orders of more than 100 samples can be priced separately. Postage is not included. You can order the analysis online and send all the samples in the same envelope.