Building materials often consist of several layers. Under a tile there may be grout, tile adhesive, filler or a waterproofing membrane. When you remove a piece for analysis, the layers of the same building element are sent together in one sample bag.
Why should the layers not be separated at home?
You cannot tell whether asbestos is present from the colour or position of a layer. If you split off and sort every thin layer yourself, part of the material that needs to be examined can be lost altogether. At the same time, the sample is handled more than necessary.
A representative piece shows the laboratory what the layer structure looks like at that spot. A piece of tile with grout and tile adhesive still attached, for example, is packed as one sample. Label the bag with the location and material, such as "Bathroom, wall tile with the layers underneath".
When do you need a second bag?
A second sample is needed when you are testing a different material structure or a clearly different spot. The bathroom wall tiles and the vinyl flooring do not belong in the same bag. Materials that differ from each other and were installed in different renovations should also be kept separate.
A good rule of thumb
Keep together the layers that come away from the same building element. Put different building elements, different materials and clearly different spots in separate bags. That keeps the sample easy to trace, and the result can be matched to the spot where the piece was taken.
If you are unsure, name the sample as practically as you can. An exact location and a description of the material matter more than giving every layer its correct technical name.