Wall filler is one of the most common asbestos-containing materials in Finnish buildings. It was used widely to level walls and ceilings before painting, papering or tiling. It is a particularly risky material when it is sanded or taken off, because filler dust becomes airborne so readily.
Why is there asbestos in wall filler?
Asbestos was added to wall fillers to improve their strength, their workability and the way they dried. The fibres reinforced the filler and stopped it cracking. That was especially welcome on large surfaces, where an even, crack-free finish mattered.
Asbestos-containing wall filler was used widely in Finland from the 1950s to the early 1990s. It was most common in the blocks of flats and public buildings of the 1960s-1980s, where large wall surfaces were levelled with factory-made filling compounds.
The particular risk of wall filler
Wall filler is a particularly dangerous source of asbestos because it so often has to be sanded or chipped off during a renovation. Sanding produces extremely fine dust that spreads through the whole room in moments and through the ventilation into other rooms as well. The asbestos fibres in that dust are far too small to see with the naked eye.
A few minutes of sanding without precautions can amount to significant asbestos exposure. That is why it matters so much to establish whether wall filler contains asbestos before it is sanded or taken off.
Multiple layers of filler
In old buildings, walls have often been filled several times over the decades. There may be several layers of filler on top of one another, each from a different period. One layer may contain asbestos while another does not.
When taking a sample, it is important to include every layer of filler, or else to test each layer separately. If you sample only the surface layer, an asbestos-containing layer beneath it goes untested. Testing the deeper layers matters especially when the wall is being taken out or sanded back to the load-bearing structure.
Taking a sample of wall filler
A wall filler sample is taken by prising a small piece of filler off the wall. Use a chisel or a knife and work carefully. Try to capture every layer of filler, not just the top one. A sample of about 2-5 centimetres is enough.
A good place to sample is the bottom of a wall, the corner of a room or anywhere else where a small mark will not be noticed. If the filler is covered with wallpaper or paint, take that surface layer off first and sample the filler itself.
Where is filler found?
Wall filler has been used in almost every kind of room: living rooms, bedrooms, kitchens, bathrooms and hallways. Ceilings were often filled too. Asbestos-containing filler is especially likely where wall surfaces were levelled smooth for painting or papering.
The walls of stairwells, cellars and storerooms may also carry asbestos-containing filler. In practice, filler can turn up in any space where the wall surfaces were worked on before 1994.
How to proceed
If you are planning to sand, take out or otherwise work on walls in an old building, take a sample of the wall filler and send it to the laboratory. You then know whether the filler contains asbestos and can work safely. Skipping the test and starting to sand without knowing is the single biggest cause of asbestos exposure in renovations.
The result of the analysis tells you whether you can carry on as normal or need the help of an asbestos removal company. Either way the information is valuable, and it helps you plan the job safely and cost-effectively.