KRed75 t1_iybsid4 wrote on November 30, 2022 at 5:35 AM

Concrete cracks. It's what it does.

You can fill the cracks with epoxy or self leveling polyurethane caulk if it makes you feel better.

One thing I highly recommend you don't do it install tile. No matter what you do, the tiles will also crack eventually.

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

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.

SturgiesYrFase t1_iycxazh wrote on November 30, 2022 at 1:56 PM

Uses to do polished concrete and decorative coatings. We had a saying:

Ice cream melts, and concrete cracks.