What is this material in 1940s home?

Saltwater

We live in a double brick, 1940s house in Sydney.  We just took out two old (presumably original) windows. The flashing and brickwork is exposed internally until the renderer and tiler visit in a few weeks time. I noticed tonight some interesting material under the flashing. It’s soft to touch, very thin and brown/grey. Same colour as the mortar hence why I only just noticed. Almost like material. Builder wasn’t sure what it was and said leave it alone - it will be covered up sooon enough. 
anyone know what it could be? Hopefully it’s not asbestos type material and not a threat sitting there in open (but not really disturbed) for next couple of weeks? 
I suppose I could just wet it down to be safe? 

MitchellMc

Hi @Saltwater,

That could be anything, from asbestos to some type of fungal growth. Regardless of what it is, if you have any suspicion something might be asbestos, the best practice is to treat it as asbestos. In this case, I'd recommend you wear some PPE gear and encapsulate that area by taping a section of builder's plastic over it with duct tape. Make sure to tape all sides of the plastic down to the wall and frame so no air can transfer. That way, any particles of it that are disturbed over the coming weeks can't become airborne. 

The only way to positively identify whether this is asbestos is to have a sample tested. You'll find some helpful information in this guide: Asbestos for households and the general public. You'll also find this factsheet useful.

Please let me know if you have any questions.

Mitchell