Master Bath Reno; Inset Shower Pan on Concrete Slab; Advice Wanted

[leavengood]

I've done a few searches but can't seem to find information specific to my situation, so I figured I would ask.

I live in South Florida in a circa 1980 wood frame house built on a concrete slab.

I've demoed my master bath down to studs and concrete floor and am currently a bit stuck on my best option for the shower pan. It is a pretty traditional 32x60" shower, but unlike most I've seen, there is about a 3 and 1/2 inch deep inset for the pan. It had no kind of waterproofing before, and the studs and insulation behind the tile on an outside wall were quite indicative of that.

I was originally going to do the traditional deck mud preslope, membrane, deck mud second layer and three part drain. But a few issues have kept me from moving forward, and then after repeatedly seeing Kerdi mentioned on these forums I have started considering that (and I would likely still do my own mud bed for it.)

Here are some of my concerns:

1. Given I have an inset, can I get away with not having a curb? In the traditional mud and liner approach it seems like this wouldn't work. I figure I need at least 3 inches at the wall for a proper slope (at least at the farthest wall, which is 33" from the drain), so that would not leave too much room below the bathroom floor level of concrete to hold much water. Also it doesn't seem ideal to be laying the extra membrane on the concrete floor versus wrapping it over a curb. Now if I went with Kerdi I would not need as much mud on the floor, so maybe using Kerdi would allow for no curb.
   
2. I have some holes in the slab in the shower and where I had to dig out to change the drain. Can I just fill those with deck mud when I'm doing a preslope or would concrete be better? Mainly I'm concerned about cure times since I've read 28 days for concrete, but maybe that is only for a whole new thick slab and not small patches.
   
3. Is a "traditional" pan fine, or would Kerdi be better? I know the latter would probably be a bit more expensive, but given how much I'm saving by doing it myself, it seems worth it if it results in a better job. Personally it also looks easier, though I've just watched a few YouTube videos so far...
   
4. Regardless of whether I do a traditional pan or Kerdi, I feel like I need to smooth out the edges of the inset because it is pretty rough from having the tile chipped out. Is deck mud best for that? But I should only add material to the same depth as drywall or concrete backer, correct? I might need to chip out more concrete in some spots, if so.

I probably can come up with more questions, but this is a good start. Thanks for any help!

Pictures to come in a follow-up post...

[leavengood]

Pictures:

1. Overall shower.
2. Drain.
3. Back Left Corner (the more rough edge.)
4. Back Right Corner
5. Front Right Corner showing inset from bathroom floor.
6. Insulation damage from water.

[leavengood]

You can also see in the 4th picture a stud which is pretty far out of true. What is the best way to fix that? In fact most of this house and quite a few parts of this bathroom were built pretty shoddy with horribly askew walls and what not...

[PC7060]

Hi Ryan, welcome to the forum.

1. I'd say you have a excellent configuration for a curb less shower.

2. If the holes penetrate through the slab I'd reinforce with rebar or wire depending on the size and fill with quikcrete. If the holes don't go through the slab I'd just fill with deck mud as I was doing the shower floor. You'll want to apply a layer of thinset down on the slab before you put the deck mud in to ensure a good bond.


3. Kerdi board and Kerdi seem like a good solution. Replace that nasty insulations first.

4. Not sure I understand but if I wanted parts of the slab smoother I'd chip it out or grind it off. Not sure what good thinset will do for you.

[PC7060]

By the way, nice working numbering your questions on your previous post.

Re the out of true studs, the is the time to replace or reinforce studs so you have a strong and true wall to work with. Really good time to add some blocking too.

[leavengood]

Hi PC,

Thanks for the answers for questions 1-3.

As for question 4, I don't know if you can tell in the pictures but the side of the inset (which is essentially the slab from the kitchen on the other side of the wall) is really rough, and doesn't seem like a good surface to put a liner or Kerdi onto. I didn't really think about taking the time to smooth it out by grinding or whatever, but I guess I could do that. What is the best tool for that?

[PC7060]

If it's the side of the inset there's no need to worry, you'll fill that up with deck mud to level with the bathroom floor along the edges sloping to the drain in the middle. Once you have a the mud floor in the Kerdi goes over the mud bed and up the wall.



If you do need to take off a little concrete, Id use a chipping hammer or a 4" grinder with a diamond blade. Get a fan in the window first because its dusty work.

[cx]

Welcome, Ryan.

Please add that geographic location to your User Profile so it will remain permanently in view to aid in answering some types of questions.

1. The direct bonded waterproofing membrane is the only practical way of dealing with what you've got in the way you want to do it. Kerdi is one such membrane, but it's not your only choice.

2. Repair the holes with concrete, making provisions for the installation of your new drain. You needn't really let that patch to cure at all before installing your deck mud if you don't wanna.

3. See #1.

4. You'll need to chip out at least the one corner we see there, but you needn't do any smoothing beyond ensuring that the concrete is not proud of a plumb line down from your stud walls so it won't bow out the bottom of the wallboard. The wallboard can be attached at the slole plate and the mud floor will support it when the membrane is applied.

Your mud floor must slope a minimum of 1/4" per horizontal foot from the farthest point from the drain, which is almost always a corner. I like to set bonding flange drains (USG, Kerdi, other) with the flange at least 3/4" above the concrete grade to allow room to pack mud under it. That would allow you something under two inches total height at your perimeter, so you'd still be able to have an inch-and-a-half step down into the shower.

My opinion; worth price charged.

[PC7060]

Ryan Ok, after reading your post again and CX's response I understand better what you are asking. I had it my head you were looking to do a curbless shower but can see it would be a challenge to get the minimum 2" drop from shower entry to the top of drain.

If you have slight step down from the bathroom floor into the shower as CX said, I can see how you'd need to clean up the edges of the slab to ensure smooth sides.

Another option is to shim out the backer board (or Kerdi or ProPanel, etc.) off the wall so it goes down the wall into the recess without any bump out due to interference with the concrete.

[leavengood]

I think my first steps before moving on to worrying about the shower pan is to fix the untrue walls and replace the bad insulation. I can probably also do whatever plumbing fixes or changes I need before I cover up the walls.

I also need to decide on what system I'm going to use for the pan so I can get the new drain installed. I have already purchased a 3 part drain and also one of those nicer square drain inserts for it, but from what I understand I need a different sort of drain for Kerdi. Since I'm working in a concrete slab I need to get the drain plumbed in before doing the pan. From what I've seen that is a bit more tricky with Kerdi...

I should probably also check out the other pan/waterproofing systems mentioned on these forums.

[PC7060]

Originally Posted by Ryan

from what I understand I need a different sort of drain for Kerdi. Since I'm working in a concrete slab I need to get the drain plumbed in before doing the pan. From what I've seen that is a bit more tricky with Kerdi...

I found the Kerdi drain install to be pretty straightforward; just need to know the plan height of the finished drain relative to the slab.

You may want to consider curb-less shower with a linear drain located on the side of the shower furthest from the opening.

With a 3/8 slope over 60" you would have the required 2" drop when you add in the height of the DITRA or backer board on the rest of the bathroom floor.

Here is a link to a very nice Curbless shower with linear drain done by Chuck Stevenson. Bigger overall bathroom than your project but you get the idea.

[cx]

Originally Posted by Ryan

Since I'm working in a concrete slab I need to get the drain plumbed in before doing the pan. From what I've seen that is a bit more tricky with Kerdi...

Not really.

When doing showers with Kerdi or USG Shower Membrane, I do not set the drain until the shower is nearly finished; ceiling and walls tiled, except for the bottom row of wall tiles, and mostly grouted. No worries about damaging the drain or waterproof pan until it's necessary to have them in there.

My opinion; worth price charged.