I built a bathroom in my basement and now I am ready to install tile. My question is I have noticed hairline cracks in the shower floor. I put down my 1st layer of concete than a rubber shower pan and than another layer of concete. Do I need to repair them and how do I do that?

BDEGGC

If you are talking about the second layer of concrete cracking, its because your mix was not correct. It should have been a 5(6) sand to 1 portland cement mixed very dry. Excessive portland or a mixture too wet will cause it to crack. That being said, if the concrete is stable and not shifting, you should be fine to install tile as is. The concrete is not meant to stop moisture in any way. It actually is designed to allow moisture through to the vinyl pan, then to the drain. Hope this helps!

hdsoftail

Thank you very much, I started to tile and all is going well. Again Thank-you

thinkaboutothers

If you have hairline cracks that means you overwatered the mix at the time of installation. The safe thing to do would be to find a crack isolation membrane to apply to the base to assure that your installation will not be damaged later on

glavine

you should have the first layer of concrete around 3" with a slop to the drain with the rubber membrane under it. after this sets you go over concrete with you mortor for the tile
now for my company we also use a fabric sealer that goes on over top of the bed of mortar. then the tile but thats so i can sleep at night lol and not worry about leaks.
if your having the hairline cracks it will most likely crack your tile, it take very little movement to crack the tile once there set, you can try and use an additive with laytex to give you some play, good luck