you Just described the same scenario I went thru...down to the the bathroom being on top of the kitchen. I went the schluter way. my shower is 36x54 and found the pan easy to work with. Word of advise is to look at other forums if you haven’t done so such as John Bridge and Terry Love, wealth of information there. Double check you joist for support. My wife wanted marble, so I had to reinforce the whole bathroom subfloor to account for deflection. Make sure you add extra support on the joist where the pan would be, wether you sister your joist or frame around it, I would recommend extra support across joist. The most important thing to do es check for LEVEL, Cannot stress this enough. If your pan is not level, you will have Water pooling issues which is the last thing you want on a Curbless application. Remember that all schluter products also come with a handbook that come in handy, and when in doubt...call schluter, they will direct you with your local area rep, I called a few times for questions/ concerns and they do help out.

Any reason why you wouldn't consider doing a curbed schluter pan/curb or do you really want the look of curbless?

I did not see the mention of curbless but I also would not rcommned cutting a preformed shower pan rework your bathroon design to work with a preformed pan IMO the best choice for Diy and one less item to have to coordinate in the bathroom. I prefer an acrylic shower base to tile so that would be my choice.

I like the 'idea' of a curbless shower. I've been in a few and thought it was a really nice design. Our master bathroom also isn't huge, it's 11.5 x 8.5 so the curbless would open it up a bit. Also, one complaint my wife and I have now is our shower is rather small. It's 31x40". I am 6'5" and she is 6'0" and we feel cramped. I can only expand the shower out to 34" at its widest due to the closet wall and feel like a 3.5" wide curb would nullify that expansion.

cetb, thanks for the reply! I would provide additional framing around the joists to provide a sturdy base to drop the subfloor 3/4" where the pan goes. My main concern with schluter pan is every video I've seen and what they seem to recommend is putting the walls in first, then the pan. Where as mortar pans have the walls usually coming down and sitting on top of the pan. Any water is deflected into the pan. With the walls not even going down to the floor and the vinyl membrane, there's no opportunity for water to make it down to the subfloor. With schluter, you're banking your entire subfloor and 1st floor drywall on a correct application of kerdiband using unmodified thinset.

JuneKnow even if I'll have the curbless shower within a glass enclosure down to the floor? I don't think I want a true walk-in shower because I've been in those and they are drafty and can be cold. We are in Pennsylvania and get some cold months. Cold showers would upset the wife :)

I will say that I learned a LOT from the Schluter videos as well as other installer videos that showed step by step how to do the install. I also found Schluter incredibly helpful, they even replied to our email questions very quickly. I will say you'll get great support from them.

I have absolutely learned a ton from the Schluter videos. I learned a lot from the Wedi videos as well but their solutions seem to be a lot more expensive. For example the Schluter pan I was designing around is $125. The Wedi one was over $600!! I am a little concerned hearing folks say a curbless is not DIY. Would like to understand that a bit more.

PS as an over 6'0 tall household over here, with a 30x58 shower (could'nt make it any bigger as we were replacing a tub) I salute you - that big shower is going to be fantastic curbed or curbless!!

"If your pan is not level, you will have Water pooling issues which is the last thing you want on a Curbless application."

The last thing you want is level. It must be properly sloped which is incorporated into the cutting of the floor joists. Can you existing floor joist system carry the weight of this system? Especially after cutting your joists?

millworkman, I am not cutting my joists. I will be framing supports around the joists and setting a layer of subfloor flush with the top of the joists to recess the shower pan 3/4". That will allow me to use a 1 1/8" pan without having too much buildup elsewhere in the bathroom. As for level flooring, for a preformed, presloped shower pan you ABSOLUTELY need a level floor. They are sloped I believe 1/8" per foot. An off-level floor will negate the slope and cause pooling. For a mortar pan sure it can be a little out of level and you can use a self-leveling product or do that with your pre-slope.

Yes I would agree if using a pan on top of the flooring system but raising this up 1-1/8" in my opinion takes the sense out of curbless.

I totally get it millworkman. What I failed to include was the rest of my bathroom floor is already built up, most of which I will be removing. I will leave the 3/4“ OSB subfloor but am removing 7/8” concrete underlayment as well as 1/4” tile. The pan will stick up 3/8” above the OSB subfloor and I will build that up with plywood and ditra uncoupling membrane.

Yes, that would have made a difference in what I typed. Good luck with the project.

You will need to do the entire bathroom as a wetroom. 34” is far from wide enough to have one with only waterproofing the shower area. Do you own a TCNA Handbook? Have you ever done structural alterations? Have you ever tiled anything before? Do you understand DCOF, L/720, EJ171, ANSI A118.4TE and A118.11, and the WHY behind Schluter doing the walls first?

Some people are well equipped to DIY. Some people show very well why they should hire someone. Your lack of understanding puts you in the last category. Unless you have a year to bone up and practice.

Schluter would be my go to and stay clear away from linear drains, they look cool and you would think drain more water, but in reality they don't and a pain to clean up.

It is doable project to diy if you are properly informed. You seem to have an idea already. You are not cutting the joist...NO ONE should be cutting joist w/o first consulting a structural engineer...I think most curbless applications on upstairs bathrooms end up building up the subfloor (you already have) to the whole bathroom to accommodate the pan as well as deflection. Which is why you need to be well informed and follow the guidelines that were mentioned here by celadon or JuneKnow (think is the same person) hence why I mentioned John bridge and terry love. Those are forums dedicated to plumbing and tiling. There is a deflection calculator that work if you have regular joist. If your joist are engendered (I-joist) the Schluter also provides info on how to build up the floor. 720 deflection is for natural stone. 360 is ok for ceramic tile. What that means is the needed material on top of the joist to minimize movement. As far as making sure sure the subfloor for the shower pan is flat is so that the actual Schluter pan can do its job of sloping the water you are well informed.
I followed the Schluter handbook and talked to the rep and so far it’s going great. You have to be at the ready when you post here I noticed. Seems like if you say DIY two or three common posters on this forum will right away chastised you for doing so assuming that bc it’s a diyer that they don’t know or are not aware of how to do things. Some of the recent post have been asking for help after their contractor did a horrible job tiling, lippage grout lines bigger than other, tile trim off or not centered, so I say better do it myself that have to deal with those issues. Here is a pick of my current shower. To clarify first and foremost, otherwise said ppl would just start saying how wrong you are and how it will fail!:
buit up to 720 deflection for natural stone. Framed around I joist and supported between joist under shower pan. Checked plumbing on drain to keep the slope necessary after the p trap. Ditra uncoupling membrane on whole bathroom. Kerdi band around all seams close to the wet areas. Marble is honed. Will be sealed and then anti slip sealer added as well. Epoxy or spektralock1 grout will be used to further keep things waterproofed. Have already ran shower head and handheld and water slopes right to drain. Best of luck!