Hi,
Just been down to the Bunglow to gauge out the kitchen floor.
This started life as +/-15mm with significant bumps which would have made tiling impossible (unless I used mosaic!!!).
Anyway, whilst marking out the low spots that need more latex, I found a few areas where the bond had failed (cracking of the screed and hollow sounding noises when tapped). Worst area was about 1m x 40cm, and a few other areas were smaller. About 2-3m2 out of 19m2 had a problem, everywhere else the screed was sound.
This was a contracted out job, so obviously I'll be raising it with the chap who did it - he's coming down Thursday or so.
But, in order to be able to have an intelligent discussion with him, would anyone be prepared to pass an opinion on my theory, which is:
The latex compound didn't take properly due to the surface either being a bit damp or friable or both. In either case, chucking down some stabiliser might seem to be a good idea, before re-applying compound to the affected areas. I'm thinking a good soaking in SBR (as PVA won't be so good in damp conditions).
I plan to overseal the whole floor with AquaSeal "Aqua Stop" (on recommendation) before tiling, which will sort out any damp issues - so all I have to worry about is that the levelling compound maintains a decent bond to the substrate.
Cheers
Tim