Filler is one of the most common asbestos-containing materials in older buildings. It was used extensively to smooth walls and ceilings before painting, wallpapering or tiling. Filler is particularly risky when sanded or demolished, because filler dust spreads easily in the air.
Why is there asbestos in filler?
Asbestos was added to fillers to improve their strength, make them easier to work with and improve how they dried. The asbestos fibres acted as reinforcement in the filler and prevented cracking. This was especially valued when large areas were filled and the result had to be smooth and free of cracks.
Filler containing asbestos is found mainly in buildings constructed or renovated before asbestos was banned in the country concerned – across the EU by 2005 at the latest, and in many countries earlier. It is particularly common in apartment buildings and public buildings, where large wall areas were finished with industrially produced fillers.
The particular risk with filler
Filler is a particularly hazardous source of asbestos because it often has to be sanded or chiselled off during renovations. Sanding produces very fine dust that spreads quickly throughout the room and, via the ventilation, to other rooms too. The asbestos fibres in the dust are so small that they cannot be seen with the naked eye.
Just a few minutes of sanding without protective measures can lead to significant asbestos exposure. That is why it is especially important to find out whether the filler contains asbestos before you sand or demolish.
Several layers of filler
In older buildings, walls were often filled several times over the decades. A wall may therefore have several layers of filler on top of one another, and each layer may date from a different period. One layer may contain asbestos and another may not.
When taking a sample, it is important to include all the layers of filler or to test each layer separately. If you only sample the top layer, a layer containing asbestos underneath goes undetected. Testing the lower layer is especially important if the wall is to be stripped or sanded right back to the bare structure.
How to take a sample of filler
You take a sample of filler by removing a small piece of filler from the wall. Use a chisel or knife and remove the piece carefully. Try to get all the layers of filler into the sample, not just the top one. A suitable sample size is about 2–5 centimetres.
A good place for the sample is, for example, the bottom edge of the wall, a corner or another spot where a small mark will not matter. If there is wallpaper or paint on the filler, remove the surface first and then take the sample from the filler itself.
Where is filler found?
Filler was used in almost every room: living rooms, bedrooms, kitchens, bathrooms and hallways. Ceilings were often filled too. Filler containing asbestos is particularly likely in rooms where the wall surfaces were filled smooth before painting or wallpapering.
Walls in stairwells, basements and storage rooms may also have filler containing asbestos. In practice, such filler can occur in any room whose wall surfaces were worked on before the asbestos ban.
What to do next
If you plan to sand, demolish or otherwise work on walls in an older building, take a sample of the filler and send it to the laboratory. Then you know for certain whether the filler contains asbestos and can work safely. Starting to sand without that knowledge is the single biggest risk of asbestos exposure in renovations.
The analysis result tells you whether you can carry on as usual or need the help of a contractor specialising in asbestos removal. Either way, the information is valuable and helps you plan the renovation safely and cost-effectively.