Thanks for the fast reply's...
When I had the building and pest inspections done, he had a look in the roof and didnt say or report any damage from the roof so I belive that it is in the slab, the place is over 33yrs old.... He said he wouldnt worry about it to much and there is a lot of shift in the soil in Townsville...
Well that "Sikaflex" sounds the go, I will just have to keep an one on it over the years...