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Old 09-10-2019, 12:05 PM   #1
ukdavid
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Curbless shower on 2nd floor

I'm a homeowner drawing my own plans for a renovation. I will be getting a tilesetter to do the job but the subfloor will be laid before he starts as I will most likely need to wait until I have some more $$$. I wanted to run this by you guys though just to be sure.

The attachment shows a cross section through the walk in shower at the walk in . I'm looking at the mortar bed thickness at the drain and wondering if it's not too thin! I don't know what the alternatives are though. If it needs to be thicker then there is no slope from the bathroom to the shower. This situation must be common though.

Also, I was not planning to use Ditra in the shower. The joist deflection there is L/422.

Thanks for your advice, David
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Old 09-10-2019, 04:48 PM   #2
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Have you thought about adding a short curb?
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Old 09-10-2019, 04:59 PM   #3
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When doing a curbless like you have, I prefer to cut out the subfloor, add blocking to the sides of the joist, reinstall subfloor (now 3/4" lower than main floor), install a Kerdi pan, then install an additional layer of subfloor in the main room to meet the height of the pan. That's probably not the answer you're looking for though. Not having enough deck mud thickness may cause an issue in the future. If you're set on using deck mud you could add a layer of plywood to the main floor to gain some height.
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Old 09-10-2019, 07:25 PM   #4
ukdavid
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Thanks for the replies.
I was hoping to not have a kerb at all, but it may be the easiest solution

Looking at my detail right now I already have the subfloor lowered. I estimate 1/2" of mud at the linear drain. How thick should it be? An inch? Meaning an extra 1/2" ply over the rest of the bathroom and a small step at the door to the hallway. Doable I suppose. This does lead me to a question though. If 1/8" thinset is ok for the rest of the bathroom why isn't 1/8" ok for the shower?

I had a quick look at Kerdi. Their biggest shower tray, KSLT1930/965S at 36" x 72", is too small. Anyway the perimerter height is 1 5/8". So with a 4% slope that means the thickness at the drain is 0". How can that be right?

Is there an alternative to mud or Kerdi?

I could have another look at the underlying structure and see if I can rework it somewhat. I'll start by seeing if I can move that tripled 2" x 8" at the drain.
The important thing that I would need to know is what is the minimum thickness at the drain if using mud. The installer will have the last say but I don't want to lower the floor etc. if it's going to be a waste of time.

Thanks again for the replies.

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Old 09-11-2019, 06:16 AM   #5
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David,

Everything I've read here suggest ya need at least an inch of mud at the drain.

In your detail it appears you have your mud layer directly on the recessed floor, and directly in contact/covering the top of the floor joists. If that's correct I don't think the mud will survive; the joists just move too much. I'm nearly certain you'd need a layer of ply first, but maybe one of the mud men will clarify.

You could possibly do this with a foam shower tray, as I did, but that too will require a layer of plywood over the top of the joists, and the floor must be level for it to drain correctly.

My approx. 42"X84" foam tray was only 1/4" ish thick at the drain, and it's a center drain. I suspect other foam trays are similar.
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Old 09-11-2019, 11:28 AM   #6
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Dan,
Thanks for the info.
I got the idea to lower the subfloor from a YouTube video by some manufacturer or seller of items used in creating shower enclosures. I cannot now remember what exactly they used to go on top of the subfloor. But the joist tops were most definitely exposed. If there was a layer of ply on top then you're back to a floor depth that hasn't changed.

I know this has to have come up before, for wheelchair bound people maybe. Hopefully others who have actually done this will chime in.

I'd be very interested to know who made the foam tray you used.

Structurally, I have a lot of leeway so I'm looking into moving the tripled 2x8 at the drain to the right enough to allow a minimum of 1" of mud and turning that blocking into a 2x6 designed beam spanning between the two sets of tripled beams.

Still, curbless showers are not new. I can't believe there hasn't been thousands built on the 2nd floor as a renovation in homes.

Thanks again,

David
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Old 09-11-2019, 01:27 PM   #7
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Just because something has been done a lot, doesn't mean it's been done right each and every time. Most showers built in spec houses are built wrong. What you're trying to do is possible, and you're asking the right questions.

USG makes custom foam shower pans. I like them, but your floor needs to be perfectly level and I agree with the other poster, you'll want a layer of ply under it (on top of joists). Click this link, lot of info there. "Shower trays with the center of the drain located less than 4 ft. from any wall will have a
perimeter thickness of 1 in. The distance from the wall to the center of drain must be at least 10 inches. Shower trays with the center of the drain
located more than 4 ft. from any wall, will have a perimeter thickness of 1-1/4 in. There is a form you draw your pan and dimensions on. Takes about a week from order to delivery, maybe quicker. I ordered mine through my local Emser tile. Comes shipped in pieces that fit together.

http://www.durockshowersystem.com/en...ower-tray.html

1. you're correct in setting blocking and recessing the subfloor as a start
2. adding a later of ply and/or Ditra/Ditra XL in the bathroom (not in the shower) will help raise your bathroom floor height to make things flow better
3. a foam pan will help keep your shower thickness to 1/2" ply + 1" foam = 1.5" shower floor thickness at perimeter.
4. If you have excess joist height (say 2x12 and a short span resulting in L700+), I suppose you could remove a little material from the top of the joists to set your shower a little lower. It doesn't seem like you have that luxury at L422, but I guess you could shave 1/4" if you ended up being right on the line, unless you also sister the joists under the shower? That doesn't seem worth it to me.
5. develop a more advanced view on floor sloping in the shower area, similar to how the complex ADA showers are built so that the curb is replaced by a 'hill' that is still able to be rolled over. This has ripple effects not worth it to most people, weird elevation changes by the vanities, uneven toilets, etc.

Seems to me you need to look at the rest of the bathroom, the transition to the hallway/bedroom, the floor thicknesses all around and decide where you want finished elevations to hit and what compromises you can accept. A short curb isn't the end of the world, solves a ton of problems, and is actually pretty helpful in the event of a backup or plugged drain. Shower receptors are the lowest point in any bathroom, when something plugs up, it is the first place you'll see water and debris.
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Old 09-11-2019, 01:34 PM   #8
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For my last project, I drew a simple sketch of all my floor sections in a row.

hallway hardwood floor : threshold : bathroom tile floor : curb : shower pan/floor.

All drawn to scale scale vertically but not left to right. That gave me a much better idea on how everything would land. In the end, I accepted having a 3/8" height change from the hallway to bathroom floor, and having a curb. It allowed me extra floor ply to keep everything solid, and made for a better end product that I know will last many years.
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Old 09-11-2019, 03:54 PM   #9
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Quote:
Originally Posted by ss3964spd
Everything I've read here suggest ya need at least an inch of mud at the drain.
Laticrete makes a modified mud (3701) that can be used thinner.
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Old 09-12-2019, 03:22 AM   #10
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For my curbless shower that is currently being built I sistered and notched my 2x10 joist with 2x8. That gives the 1 3/4 inch difference in height required by schluter shower pan.

Sistering and notching of joists is easy and was done in an afternoon. Much harder is dealing with the implications of removing subfloor. Your joists are unlikely to be under the bathroom walls so you will need to figure out how to support that area.

You already are at 2x8 joists so I don't know if you could do the same. One thing to keep in mind is that a 2 inch PVC pipe outer diameter is the same as the max sized hole you can drill in a 2x8. Account for the plumbing in your plans.
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Old 09-12-2019, 05:59 AM   #11
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David, Matt covered the custom size Durock foam tray particulars perfectly, and that's what I based my curbless shower floor on. I, too, had to recess the first layer of 3/4" subfloor down between the joists, which also offered the opportunity to make the entire bathroom floor both flat and level. My situation is a little bit different in that there is a pronounced hump in the floor in the bedroom at the doorway to the bath, which worked in my favor by adding about 1/2" in height, so I have no elevation change between the two finished floors.

My project is also nearly finished, waiting on the shower glass. I really, really like the curbless look, and not having a curb should reduce cleaning efforts.
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Old 09-12-2019, 07:55 AM   #12
ukdavid
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Everyone,
Thanks for the replies - very much appreciated.
I'm currently working on redesigning the joist/beam layout to give me a level but lowered area over the full shower area. It's hard though as the beams have to span over 14' and although they're strong enough using engineered lumber it's difficult to get to L/360 when working around a floor depth of 7 1/4". I'm working on it now and let you all know in a day or two and I'm keeping all your ideas and advice in mind.

Thanks again, David
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Old 09-17-2019, 05:08 PM   #13
ukdavid
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I went to see about the foam pan using that durock shower systems website but they haven't gotten back to me yet.
Anyway, I think the attachment shows what I plan to do structure wise. It needed two small foundations in the crawlspace though. Every member that is loaded by the shower in any way has a deflection > L/360, so that's good.

Thanks everybody for your help.

David
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