Asbestos Tap / Knock Test

This is more of a random question (not sure which part of the forum to put it in) but I went to inspect some houses with my dad recently (who's been renovating bathrooms/kitchens for 20+years).

I remember one house where he tapped the wall with his knuckles (like knocking on it) and he pretty much just indicated that there was asbestos here.

I asked how he knows and he said it's just the sound the wall makes when he does it versus one that doesn't.

Just wanted to ask how legitimate this is and if anyone else has heard of this 'technique' (being the complete noob I am).

 

Ask him why did he knock there?

He may well have suspicious on account of other things as well.

Does he water divine too?

I personally wouldn't touch old blue crumbly asbestos, causing particles to dislodge. But white asbestos in panels might be ok, only that would be tougher to identify ( contains asbestos? Not necessarily made of )

Love to know the answer to this

 

It sounded hollow, could be fibre cement as well.

The test requires destructive sampling and microscopic analysis (or exposure of the rear to find the label "this product does NOT contain asbestos" which was stamped after the early 1980's.

 

i would say your Father is correct ,asbestos sheets depending on the frame have a different sound compared to other walls..

 

I think knocking could help indicate if it might possibly be fibro asbestos cement. As compared to hardboard or plasterboard or brick.

But only a proper test can tell the difference between a old cement board lining that does have asbestos and an old cement board lining that doesn’t have asbestos.

 

Old asbestos sheeting may "ring " when tapped more so than newer cement sheeting. Its just one test and is highly subjective. I wouldnt be using as a test of safety. All cement sheeting MUST be treated as if it contains asbestos and also has some handling and disposal rules and cant go to general fill to avoid error and misuse

https://www.thehills.nsw.gov.au/fil...es/guide_for_renovators_-_fibro__asbestos.pdf

 

I'll give him an ask next time I go inspecting with him again!

 

Also thanks all for the replies - definitely pretty interesting to me and of course not completely reliable!