Commercial properties now have an asbestos register so builders can look and see before starting work, but even now residential property doesn’t need this – so unless the builders are aware and request a test it doesn’t get done. Testing consists of bulk samples – where a piece of suspected material (thumbnail size) is taken to a lab and analysed. This costs around £30 today, as asbestos is dangerous when its airborn, then air sampling (testing) for that involves placing pumps which suck in air over a perieod of time (say 4 hours) and then analysing the results – this costs £300+. I suspect that if this was carried out while your friend was living there she would have known about it – and the builder would have mentioned it. The most dangerous sort of asbestos is the soft crumbly sort that often surrounds heating pipes as lagging (although not all lagging contains asbestos, indeed its outlawed now).

This is a good question that everyone who renovates an old house should be asking.