Asbestos in walls: filler, board or tile adhesive?

Asbestos in a wall is usually found in one of the surface layers: filler, paint or sprayed texture coating, tile adhesive or mortar, wall boards, or wallpaper paste. In a wall built or renovated before 1994, asbestos can be in any of these layers, and it cannot be identified by eye. You get certainty by taking a sample that includes every layer and having it analysed in a laboratory.

This article walks through the typical layers of a wall, how to choose where to sample, how to take one sample of the whole layer build-up, and what the result means for your renovation.

Which layer of the wall can contain asbestos?

An old wall is rarely a single material. The surface often has several layers from different decades, and each of them may be a different product. That is why one layer alone tells you little about the whole wall.

Fillers

Wall and ceiling fillers are among the most common materials that used to contain asbestos. There are often several thin coats of filler on top of each other, and an old filler can be hidden under a newer surface. Read more in the article asbestos in wall filler.

Paints and sprayed coatings

Some old paints, and especially sprayed, rough or patterned surface coatings, can contain asbestos. A grainy or textured wall surface is a good reason to test the material before it is scraped or sanded.

Tile adhesives and mortars

The adhesive behind wall tiles in bathrooms, saunas and kitchens, as well as grout and bedding mortar, can contain asbestos. The tile itself is rarely the deciding layer: what matters is the adhesive and filler layer underneath it. More on this in the article asbestos in tile adhesive.

Wall boards

An asbestos board in a wall is possible especially in wet rooms, technical spaces, fire-protected areas and old claddings. A hard, grey, fibrous board should be tested before it is drilled, sawn or removed. The board may also be covered with filler, paint or tiles, which are layers of their own.

Wallpaper paste

Under old wallpaper there is often a layer of paste and filler. Wallpaper paste can also contain asbestos, so it is best to strip the wallpaper and sand the surface only after the layers underneath have been tested.

When should a wall be tested?

A wall should be tested before its surface is sanded, chiselled, drilled extensively or demolished, if the building or the wall surfaces date from before 1994. An intact, undisturbed wall surface does not release fibres into the air. The risk arises only when the material breaks and dust comes loose. That is why removing tiles, sanding old filler and sawing wall boards are situations where it pays to get the facts before work starts.

Where on the wall should the asbestos sample be taken?

Take the sample from the spot you plan to demolish, sand or drill. The sample must represent the material build-up that the work concerns.

• First look at which layers the wall has. A small damaged spot, the edge of a socket or an area that has already come loose often shows the layer build-up.
• If different parts of the wall have different surfaces, for example a tiled lower part and a painted upper part, take a separate sample from each.
• If the wall has been repaired at different times, patched areas may have a different filler from the rest. A good rule of thumb is one sample per different material build-up.
• If the wall is made of board, take the sample through the surface layers so that a piece of the board comes with it.

How do you take one sample that includes every layer?

The aim of a wall asbestos sample is to get a piece of every layer, from the top coat of paint down to the substrate, into the same bag. The laboratory can then examine the whole build-up at once, and an asbestos-containing layer is not missed.

1. Wear disposable gloves and preferably a respirator of at least class FFP3.
2. Lightly mist the sampling spot with a spray bottle to keep dust to a minimum.
3. Using a knife or chisel, remove a piece of about 2–5 centimetres, deep enough that every layer comes off down to the substrate.
4. Drop the piece straight into a zip-lock bag, seal it and put it inside a second bag.
5. Mark the bag with the sample location, for example "bathroom, east wall, under the tiles".
6. Cover the sampling spot with tape and wipe the area with a damp cloth.

More detailed instructions on tools and packing are in the article how to take an asbestos sample.

What does the result of a wall asbestos sample mean?

Onelab analyses the sample with a JEOL SEM-EDS electron microscope, 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 layers of the sample. The result applies to the sampling spot and similar material. Other surfaces and repaired areas of the wall are tested separately.
• Asbestos detected: because the sample contains every layer, the surface build-up of the wall is treated as asbestos-containing, even if asbestos is in only one thin layer. Demolition and sanding are planned as asbestos work, and the removal is carried out by a company authorised for asbestos removal work.

If the wall is 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.

How much does the analysis of a wall asbestos sample 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.