I am remodeling a first floor bathroom and the concrete for my shower drops down 3 inches from floor level. What kind of prep do I need before tiling the shower?

A contractor said all I need was sand mix to make the bed and didn't need a liner. I was thinking of applying RedGuard to the walls and floor. If I RegGuard on top the sand mix bed can I tile directly over that or do I need another layer of sand mix?

  • You may want to consider one of precast shower pan options such as kerdi. They have a membrane built in, you just need to seal the seams and any screw heads.
    – Alaska Man
    Jan 30, 2018 at 0:42

4 Answers 4


I would probably still put a liner in. It doesn't hurt to have, and a liner makes sure all the water goes where you want it to go. You can use RedGuard in place of a shower pan liner, but make sure you read the product instructions on how to achieve the correct thickness. I believe it's 2 coats of product to meet the requirements for a pan liner.

You can also mortar/tile directly over RedGuard (in fact, you have to - RedGuard is not meant to be left as a finished surface).


My situation is not exactly similar to yours, but may provide alternatives.

I remodeled with Durock Cement Board on the walls.

I stopped the Durock about an inch above the plywood sub-floor.

My tile guy wanted a rubberized liner over the sub-floor which my plumber installed up and under the Durock.

The tile guy then mudded over the liner and laid tile over the mud.

My tile guy didn't want me to use RedGuard he used "better stuff" over the joints. (I think tile guy just wanted to upsell the job.) He did not coat the floor.

In my amatuer opinion, you could build the sub-floor up to the level you want this way and then mud/tile.

FYI my shower has never leaked.

My 2 cents


you can red guard over the mortar bed if you like, however if u do that, be sure you use a bonded flange shower drain. they are made for that type of water proffing application.


We see drop down concrete pans here in Florida quite often. As long as the drain is 1 1/2" below the main foundation it is considered acceptable without a rubber liner. The trough created by the sunken concrete is adequate to contain the water from shower use. Cement board is created to be water resistant and is acceptable on the walls as the substrate. RedGuard on the walls is a good precaution but not absolutely necessary if the cement board is taped and prepped properly. The water will hit the surface of the tiled wall and fall down the surface. It's not going to try and seek a hole to go thru so if the set up is done right, there will be no issues. RedGuard on the pan is definitely not necessary. It may even be detrimental to the final product.

  • Thanks for the answer, and welcome to Home Improvement!
    – IronEagle
    Mar 16, 2020 at 13:42

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