Building shower curb directly on concrete

Question

I am getting ready to remodel my basement shower and wanted to get everyone's input on building up the shower curb.

My shower is located in the basement where the floor is concrete. My concern was building up the shower curb directly on that concrete. I know the alternatives (i.e: kerdie or cement) but I wanted to build the shower curb up using 2x4s.

I was against using pressure treated wood as I get concerned that the shrinking of that wood would potentially break the tile I use on the curb. Ideally I could use untreated wood with a vaper barrier but I wasn't sure if this was a common practice or not?

I wanted to get folks thoughts on the best way to build out the shower curb using untreated wood.

Thanks in advanced :)

Answer 1

Using untreated wood is ok if you are diligent about shielding it from any water.

                                OR

You can build your curb from bricks or concrete blocks ( not the 8x16, but the smaller cap blocks).

I have built shower curbs from all three and from PT wood that I allowed to acclimate for a week or so.

The easiest is the bricks. Set in modified thinset, 2 bricks high is about the perfect height after a 3/4" sill plate is added on top.

Using any wood you have to add a barrier on the shower side and then get that bonded to the floor. The alternative is a full PVC liner. That is extra expense and work. It is far easier to use bricks or blocks and coat the floor, walls and curb with Red-Guard or AquaDefense. That waterproofing also acts as an uncoupling agent. (Done this way I never had tiles crack, or a leak problem.)

Answer 2

Pressure treated wood needs to dry out really well and will usually warp in the process so yes, stay away from it. You'd want to at least seal any untreated wood with a good sealer.

Not sure why you're stuck on using 2x4s unless covering them with cement board or just pouring the curb with cement. Wood is flexible and the slightest movement will crack tile.