I recently floated a shower pan using Quickcrete sand mix. This was done on an already formed shower base (sunk about 5 inchs) concrete slab. I used a latex fortifier in the sand mix and I thought all had gone well until two days later when I checked it, the sand mix had not adhered to the concrete base and had almost warped up in a couple corners. This was laid about 2.5 inchs deep at the edges and as much as an inch at the drain. In fact, tapping around the base, it was evident it had not adhered anywhere. This was proven when I decided to pull up the pan and it was way too easy just peeling off the concrete slab. Should I have used a bonding agent? Was there some other prep I should have done to the concrete base to prevent the lifting? In reading the Quickcrete instructions, it stated I couldn't use both the bonding agent and the fortifier. Any advice on what I should have done would be appreciated.

Hi Mtnbkr

I can't see the existing concrete pan, but I don't usually save these unless I am sure I am putting a new vinyl liner over the old pan... are you?

Is the existing concrete base sloped to the drain? If not, you need to lay the concrete/cement so that the base slopes to the drain. Then you would install a layer of tar paper down (protects vinyl liner) and install a vinyl liner and proper drain assembly (so separation is not such a major issue, right?).

Next, you would TEST the water tightness of the pan by closing off the drain and filling the pan to set overnight... check for leaks.

Install gravel rocks around the drain weep holes and then install concrete/cement and if you want, install some chicken wire for added strength... slope the floor to about 1/4" pitch per foot (like you did in your last pan).

I would recommend a THICK FLOOR MUD for your shower pan... sold at most tile stores... guaranteed not to crack.

That's my thoughts. If you'd like to discuss more just let me know, OK?

Mark

You should have taken a chipping hammer and chip the existing concrete floor all over. Then, give it a coat of Concrete Bonding Agent. Proceed with installing concrete reinforcement steel and pour your new concrete slab.

However, it is not recommended to install slab less then 3 1/2" thick. Anything less will make new concrete to crack very easily. I suggest you use 5000 psi concrete mix for this application.

As far as steel reinforcement goes, you can use 10x6 wire mesh or 3/8" rebarts. You can even pre-drill several holes in existing concrete and epoxy 3/8" rebars to it. Bend them when dry and attach rest of the rebars to it.

Hope that helps. Back to you. Millo