F
Feeney
I have an approximately 30sqm kitchen floor to re-tile after lifting cracked tiles. House new build 2006 with finished concrete floor put in one continuous layer throughout downstairs over underfloor heating pipes and then the walls built up from there (so no expansion gaps between rooms). The underfloor heating system was incorrectly installed without a thermostat so the water was circulating underneath the floor at way too high a temperature. This resulted in substantial cracks throughout the concrete which cracked so many of the tiles I had laid we just decided to lift them and start again. The heating problem was sorted three years ago and I am as satisfied as I can be that no new cracks have developed since then. The cracks are basically 2 distinct fault lines that run approximately in a direct line from each of the four walls to the opposite wall with a few shorter cracklines which branch off the main one. At their worst they were almost half a centimetre wide but mostly about 1.5 to 3mm wide. The tiler I have been working with put down levelling compound 2 months ago in prep for retiling (latex based - the one you get the liquid separately and mix before applying - it was suitable for use with underfloor heating). NO other product was used or prep to the cracked concrete 1st (such as scraping it out and filling with some special product). 2 months later, hairline cracks have emerged in the same place as the original ones. I cannot risk tiling until we are satisfied that the new tiles won't also crack. I have considered using ditra matting but apart from the cost that would raise the finished floor level by up to .5cm which I want to avoid if I can. I realise now I should have made sure the cracks were treated first before pouring the levelling compound. However, I am hoping that it may still be possible to do that now. I am speculating that as the fluid in the leveller dried out, the leveller kind of subsided into or shrunk inside the cracks leaving the surface to crack as it dropped down. I am wondering if it would be possible to 'scrape' or excavate out along the path of the hairline cracks that have appeared now to make a crevice which could then be refilled with some kind of flexible product. Any advice greatly appreciated!
