Where do you find these?
Textured coatings were used to produce decorative finishes on ceilings and walls. In the past, they have had various trade names such as 'Artex'.
What do these look like?
This is dependent on the particular decorative finish required ie peaks or patterns. They are hard and were originally white in colour but have often been painted over.
How dangerous are these?
Work on any type of asbestos can be dangerous. However, work on textured coatings can be carried out by non-licensed workers who are appropriately trained. This work would generally not need to be notified.
If the work is likely to cause significant break up and deterioration of the material such as large scale removal using steaming or gelling methods, then notification would be required.
Asbestos essentials includes a number of task sheets which will show you how to safely carry out non-licensed work on textured coatings.