shower curb grout cracking
In December of 2009 we finished renovating our bathroom. The shower was installed with a wood curb on a concrete floor in the basement. I know the contractor took a long time to install the shower floor and had water sitting in the shower stall for 24 hrs to make sure it is not leaking before he continued to finish the curb. The only thing that concerned me at that time was that he had to move the drain for the shower from where it was and he opened the concrete flooring to do so for maybe one foot. He started to install the shower curb and shower bottom on top of the opened concrete, he only closed the opening with some plastic and didn't close it with concrete anymore. When i asked him about it, he said that this is fine and there is nothing to worry about since the foundation is all gravel underneath the house and the shower will be sitting on top of the opening.
About one year after renovating I realized that the grout on the outside of the shower curb started to crack. i didn't think it was serious since it was outside and not inside where it gets wet. The grout continued to crack from the corner all the way to the wall. See pictures attached. One week ago though, i noticed that the grout inside the shower is starting to crack now too. It has been over 3 yrs now since the renovations.
there are no other cracks in the shower floor or on the walls.
could the cracking of the grout be from moisture from the opening of the concrete floor under the shower? i don't think the shower itself is leaking since it seemed to me that it was installed properly and also looking at the time frame of three years. I must say though that this particular shower in the basement only gets used about 2-3 times weekly.
Thank you for any advise,