Helgafjell4Me t1_iybv5l9 wrote on November 30, 2022 at 6:04 AM

Reply to comment by KRed75 in Found cracks in concrete slab, how worried should we be? by fireaway199

You can prevent that by properly leveling the floor and then using an isolating or "decoupling" underlayment like Ditra over the concrete. Any major movements are likely done happening for a 30 year old slab. Minor movements can still happen and Ditra helps protect the tiles by providing some level of elasticity underneath the tile. Where I think you can about guarantee cracks is over a relatively fresh slab that's not done settling, especially if you don't use the protective underlayment.

KRed75 t1_iybx21q wrote on November 30, 2022 at 6:26 AM

You can only try to mitigate cracking using schluter ditra. I've had to warranty cracked tiles laid over schluter ditra on numerous occasions. We no longer install any tiles over a concrete substrate even with ditra.

Hypotheticall t1_iyd1ueg wrote on November 30, 2022 at 2:32 PM

I'm assuming you don't do wood either, or any substrate then?

Helgafjell4Me t1_iye2plb wrote on November 30, 2022 at 6:36 PM

I'm curious what types of flooring you do use over slab then? I did tile over ditra in my master bath, there weren't any cracks in the slab, so I'm not worried about it cracking in there, did it mostly for waterproofing and a tiny bit of thermal insulation. I do still have about 1200 sft of slab floor that will need to be redone in my kitchen/dining/laundry/living area. I know I don't want to tile all of it, maybe none of it, but the best I can come up with is luxury vinyl planks (it needs to be waterproof, not just water resistant). Problem is the floor needs to be relatively flat and I can't use any underlayment with that stuff apparently. I'm confused why LVP doesn't allow underlayment when laminate planks do. I could just do LVP in the kitchen area and stick with carpet in the living area, but really would like to ditch the carpet. Large area over a likely unlevel and cracked slab is a problem though. I'm surprise there doesn't seem to be better options.