I am in the process of building a tile shower. 34 x 48. I will be using the
pre-sloped styro base with the membrane/drain kit etc.

The underlayment is not flat/level and has a gradual slop of about 1/8-1/4(Rough guess based upon my initial level reading). It starts about 3/4's of the way and not the whole length of the shower.

I was planning on putting a 1/4 Hardibacker board on the floor also for additional support over the 3/4 particle board as I have to patch the drain area where the plumber did some work. (I will be replacing a section of particle board and then the HB board)

Long story short, what is the best method to level. Use a self-leveling compound or can I use a thinset to smooth out? Should I level on the particle board or install the HB and then level?

Thanks.

Are you sure this is particle board and not OSB?

Particle board looks like compressed sawdust, because that's basically what it is. OSB looks like chunks and strands of wood. There's a distinct difference in the two. While neither of them are as good as plywood in my opinion, OSB is light years ahead of particle board in stability and strength.

If you do have particle board, you will want to remove it and replace it with OSB or plywood. A little bit of water will cause particle board to swell to several times its original thickness, then deteriorate and fall apart. You definitely don't want something this unstable under your shower.

If you do have to remove it, you will be better off getting your floor level and flat from the joists up. This will also give you the opportunity to take care of those areas that now need patching. You don't want to use 1/4" hardibacker for repairs as it doesn't have the strength of plywood and OSB.

Sorry. It's OSB. 3/4 subfloor. I am going to cut a small section out to patch the small opening the plumber created. I will patch with the same OSB and then cover the OSB with HB. (Sorry if I wasn't clear as I know HD doesn't have the structural strength. I want to avoid having to cut the entire subfloor out as it seems it should be able to be leveled without doing this.

Given my clarification, what's the best way to proceed? Thinset then HB, HB then thinset, or thinset and let it cure and then just apply another layer of thinset to set the styro pan?

Sorry for the confusion.....

Ideally, you would use a mud preslope which would take care of the unlevel floor. If that's not an option for you, then you can use thinset to level it, provided you don't build it up more than 1/4". You may have to let it dry more than a day.

There's really no use for the Hardibacker that I'm aware of, unless the manufacturer of that styro base requires it.

Is this a Kerdi shower?

It's a Prova Shower Kit. As I can tell and be told similar to the Kerdi. It was just easier for me to get access to.

Correct. I don't have to have HB for based upon the installation directions, I just thought it would provide a more "refined based." However, more work on my part....

I most likely with use the thinset to level the areas.

Anything else I should be aware of?

I'd say the Hardi is definitely optional for you, then.

Best advice I can give you: Take your time. If you feel like you're going to have to rush the project or any part of it to get it done on a certain schedule, wait until you have more time. Nothing worse than looking every day at some job you did and wishing you had done it better.

Thanks for the tip. It's a bathroom remodel for our family. We have other bathrooms we can use and it doesn't have to be done on any certain time schedule. I am thankful for at least that much. I have done enough tiling to feel confident, however, not with a shower and water. So I want to make sure I get it right even if it takes me 5x's as long.

Thanks for the prompt replies. I am sure I will have other questions as I proceed.

Sounds to me you have a hole around the drain that is a little too large. I recommend installing some 3/8" ply. Level the floor with thin set if it's not off too much. Hardie will do you no good.

Jaz

Jaz

Correct.

The area around the drain was too large to start and then the plumber had to cut out another section to center the drain, making the hole irregular.

Are you saying to level the floor and then the 3/8 plywood over the whole base? (Not patching)

I was going to just cut/patch, make the drain area tighter, level, and then install the HB just as a final surface. I know it can't be used as a structural support.

The 3/8's plywood sounds like a better option....

Hardie will do no good under deck mud, use plywood if needed. 3/8" would be the minimum, thicker is better, all depends on how large that hole is.

Level the floor after you install the plywood.

Jaz

You need to get rid of the particle board completely, sorry but you can't install anything over which may leak water !

He doesn't have particle board, but OSB. This is an acceptable substrate for a styrofoam shower pan.

I agree with Jaz, use the 3/8" plywood, cut the appropriate size furring strips based on on your slope at the perimeter of the shower pan, then screw the plywood down at perimeter and at shower drain,to create your pre-slope, even though your floor is not level, you should be close enough to pass inspection after your shower pan material is installed

Similar but different problem...

I have a shower in a basement that was being remodeled when I bought the house. Shower is studded out and covered with cement board. Structure is very sturdy and with the cement board, it’s very solid. The only problem is, I noticed when I put the level on it that some of the areas are not completely level. I don’t want to tear it all out so I thought I could correct. The most it’s off is about ½ in a few places. One option I thought of would be to mud all the walls, but that might be over kill. So, could I do one or two walls to correct the problem? Or can I fix it with thin set? And how?

My next issue is waterproofing, I can fix some of the joints but would feel a lot better just applying Kerdi to the surface to give me peace of mind that everything is sealed. Can I do this if you suggest I use mud on the walls to fix the alignment? I still have to complete the mud deck since it is just a pipe coming out of a concrete floor. Since it is custom shower size I can’t us a pre made pan.

Any help would be appreciated.

Furring out a tapered wall with mud is best left to the pros, even for us it's a difficult task. Far easier to take off the cement board and sister all the studs so that he new ones are plumb. If the cement board is screwed on this should only take a couple of hours. you could also cut tapered furring strips, but at $2 or 3 for a 2x4 it hardly seems worth it.

I agree with Jaz, use the 3/8" plywood, this will work, you can also use the plywood as your pre slope if you install furring strips at the shower perimeter according to the slope required.