Tiling on debonded screed

[crisis123]

Hi
I am after some advice about what to do in a kitchen/ family room in a house I recently moved into. Part of the kitchen and all of the family room is an extension. The floor in the extension consists of a concrete sub floor with a 50mm thick sand cement screed on top. The floor sounds hollow when tapped. I broke out the floor screed in the extended end of the utility room, it turned out the screed itself was sound, it just wasn't bonded to the sub floor. I am guessing that the kitchen/family room will be the same, as there isn't any cracking in the screed, just the hollow sound.
I am planning to lay 10mm thick 600x600 tiles throughout and would like to know if it is essential that I break out and relay the screed, or would tiling over it be ok?

Any help and guidance would be appreciated.

Thanks

Crisis

[whitebeam]

Hi and welcome..

If the screed is hollow then it will crack at some point, replace before any tiling..

[Ajax123]

This method of construction i.e. Screed direct to concrete with no mechanical preparation, is called unbonded construction. The minimum depth should be 50mm and the maximum bay size should be 36m2with maximum aspect ratio of 2:1. Th design depth should be 65mm to compensate for uneven ness in the substrate but let us assume in this instance it was flat. The only reason for it being hollow if as you say it is sound will be a reult of curling. As already suggested it is likely that the end result of this curling will be some cracks appearing as the screed ultimatly "gives" under compression loading. This type of movement will deffinitely take the tile face with it. My opinion is that whilst it may appear sound it has not been properly cured hence the curling. It may not be as sound as you think. This can be tested but in all honesty given what you have described i would remove it and replace it with a better sreed tht can be laid thinner perhaps without curling issues.