sweating screed and very porous stone - that is the problem - get a dense stone and sweating screed and it won't be a problem - again this is not a problem when fixed in S&C so maybe it is the modern adhesives?
hard to nail this down to one problem, think its a combination of two or three of the above, the screed seemed absolutely dry when i first looked at the job, and the builder that Ive done lots of work for before was happy that the screed was dry enough to tile, I didnt, and have never used a damp meter to test screeds, and when in doubt, use the old fashioned method of leaving a tile on the screed overnight, and check for even colour when lifted.
All tiles are still well adhered, after near three week of fixing with UFH being turned on for 7 days.
I am more swayed to believe that the extended set adhesive, perhaps being mixed slighty wetter than specified, to help ensure a consistent bed, and a porous tile sucking the moisture is a more likely explanation.
When Instamac were first contacted by my adhesive suppliers, about the use of extended set adhesives with light coloured stone, their first reaction was to say that rapid setting adhesive would be a better product, but on the front of their bags of extended set, its states "Suitable for natural stone".
If its not suitable for all natural stone, it should be stated on the bag.
From previous posts I was beginning to believe the problem may have been caused by a damp screed bleeding moisture, and still maybe a contributing factor, impossible to know the truth about mix percentages in screeds, drying times and conditions, when presented with what seems to be a ready floor.
The suppliers of the adhesive, a very reputable company, that I have worked very closely with for over twenty years, have only come across this problem once before with the same tile and adhesive, but was with wall tiles, so issues of wet screeds cant be blamed, and power clean was used and seemed to rectify the problem after a relatively short time.
These same guys, have been fantastic in trying to solve the issue, they didnt supply the stone, but have contacted the adhesive manufacturer, stone suppliers and liaised with me on solving the issue.
I personally think its a combination of slightly wetter mixed extended set adhesive, with a very porous poor batch of stone, with cold fixing temps.
Not having extensive experience of any of the above, i dont have the ability to identify the cause.
Very frustrating.
A straight forward job, fixed in the same fashion i would fix any other job, has gone very wrong.
I'm very conscientious, never have issues with my work, but am tired of being told
" stop worrying, its not your fault, you've done nothing wrong".
Need this problem rectified.
