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Old 06-07-2017, 12:23 PM   #1
DanWrghtn
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Shower mud pan

This would be my very first mud shower pan. I understand the process but just don't think I could do it within the 30 to 45 minutes one has to work the mud. I'll be using a Kerdi drain and Kerdi waterproofing throughout the shower. I understand how to set the drain with just slightly moister mud than is used for the rest of the pan. I had wanted to use a Kerdi tray but the drain is enough off centered (set in concrete floor) so that when cutting the tray to fit, it would leave slightly differing perimeter heights.

Questions regarding mud pan:
Can the mud pan be done in 2 sections? Perhaps from the wall just to half the drain and then right after do another mix and finish the job OR would it be best to wait longer to do the 2nd half ... if this method would even work ??? I guess I could put some thin "rebar" into the first half sticking out to solidify it with the 2nd half ??? Just thinking as a write.

Or, is it possible to use several pre-cut 1" or 2" wide "sticks" from wall at the same perimeter height, each with their respective slope to the drain, and use these as "guides" (or are they called "screeds") and then pull them out and fill in the gaps? I think in this way I could do it within about 30 minutes.

Questions if I were to use a Kerdi tray:
Shortest distance to middle of drain is 16"; Longest distance is 23" (from furthest wall; diagonally from corner would be even more). Difference is 7". On a 1/4" per ft. slope am I correct to assume there would be a perimeter height difference of a hair over 1/8" (about 9/64) or am I way off. If it would be a hair over 1/8"... is this tolerable? Could at least say 1/16" be made up for with a little extra thinset either under the tray on one side or floor tiles or both?

If you want a decent floor to wall transition, what would be the maximum perimeter height difference in the pan that wouldn't be noticeable after tiling and grouting?
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Old 06-07-2017, 07:00 PM   #2
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One thing you can do to speed things up is to install a small mud screed around the perimeter of the shower using a level. Put a little thinset down under the mud to help it bond around the perimeter, doing one wall at a time. Once you tap the level down into the mud and get it level, cut the mud back with a margin trowel leaving a small curb (screed) about 1 inch wide all the way around. Let that set and then mud the center area the next day (or whenever you get to it). Having the small screed already hard will help you when mudding the center area.

When mudding the center area, your drain and screed will already be set. Just apply thinset, then mud in an area and work your way around filling in from point A to point B. Have several boards cut different lengths to carve the mud with since the drain is off center. Keep one end of the stick pointed at the drain at all times as you carve the mud. Once you get the mud carved like you want, go over it with a steel trowel to knock down any crumbs or small hills. This will also slick down the surface and keep it from eroding so easily.
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Old 06-07-2017, 09:14 PM   #3
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I am just an amateur and depend on all these fine posters to help me....Just do it....it aint that bad...you will have plenty of time
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Old 06-07-2017, 09:53 PM   #4
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Like Tracy said, you have more than 30-45 minutes, at least an hour. Get a friend to help. You don't have to mix all the mud at one time. You can be using the first batch while your friend is mixing the second. Plus, you can mix a couple batches dry and let them sit a while and then add water when you're ready. I'm not saying to mix them dry the day before you need them, just a couple hours in advance won't hurt anything.
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Old 06-07-2017, 10:34 PM   #5
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I see what davy means the mud screed will be covered up by the cement board and thinset/tile on the wall so there is no cold joint. its getting covered with kerdi so no matter anyways. realized kerdi drain requires no preslope so you dont need to use trick sticks just regular straight screed boards
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Old 06-07-2017, 11:53 PM   #6
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Thumbs up Thanks so much!

Thanks so much Davy and all. Really appreciate the tips, advice and encouragement. It's just that since we had the home built we've 2 installers do a very poor job. I'm aiming to get as much information as I can before starting. These are great forums for that.
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Old 06-09-2017, 09:41 PM   #7
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Question Removed old pan; trowel lines remain

Real quick. I removed an old KBRS foam/fiberglass shower pan. I'll be making a mud pan and then all Kerdi. The old thinset and trowel "lines" remain on the cement floor which is a bear to remove. Is it acceptable to just put the mud on top of the old thinset / thinset lines? Or, should I use a self leveler over, let it dry and then the mud pan? Or, do I have to make the extra effort to remove the previous thinset?

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Old 06-09-2017, 10:00 PM   #8
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Dan, let's keep all questions related to this project on this thread so that questions and answers aren't duplicated, and the history is in one place.

You should be bonding the mud to the slab with a slurry of thinset. In your case, if the old thinset is stuck down well, I'd skim over it with the flat side of the trowel, then comb notches out immediately before putting mud down. No need to remove the old thinset in this case.
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Old 06-10-2017, 09:22 PM   #9
DanWrghtn
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Terminology

Thanks Kevin. I just want to be sure I understand the terminology before proceeding.

Skim:
Does "skim" over kind of mean like leave a light coat or leave a light coat while also filling in the previous thinset notches/grooves?

Comb notches out:
Does "comb" the notches out mean removing most of the fresh thinset from the grooves using a trowel or some other tool ... or an actual comb?

Is the idea to leave a thin coat of fresh thinset just not a thick amount in the grooves/notches?
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Old 06-10-2017, 10:43 PM   #10
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skim means to leave a very light layer of thinset keyed and ontop of the old thinset. if you leave a bit more ontop by skimming it wont dry out on you as quick then you comb out the thinset ontop of that before packing in the mud.
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Old 06-10-2017, 10:49 PM   #11
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you would want to completely fill in the groves
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Old 06-11-2017, 12:44 AM   #12
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Figure out your drain height and edge height before you get started. Mark the edges with level lines before you start mixing up mortar. I use a sharpie or white grease pen. Just use something that stands out.
Do it like this video, Except you are on concrete. (versus wood in the video)
Make sure your old thinset if clean, vacuum and wipe down with a wet sponge. let dry. Precut some expanded metal to fit in the pan. Be sure to cut it in such a way that allows you to tuck it under the drain flange a little bit. Its okay if you cut it into 2 pieces, as long as you overlap it.
Skim the whole area with thinset using the flatside of trowel. Like frosting a cake, ask the wife to help if you are one of those guys that refuse to cook. Then trowel in some notches. I usually use a 1/4x1/4 trowel, I am sure that I will get scolded for this. Lay your expanded metal into the thinset. I like using wall float/fat mud for under the drain and for around the perimeter of the pan..
You will have more like 90 mins plus. It doesn't need to be perfect, but you do need slope towards the drains.
You will end up filling in holes and low spots with thinset when you install the the membrane on the floor. Then you sort of do it again before installing tile.
You got this.

https://www.youtube.com/watch?v=SVaPHoYkU-U
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Old 06-11-2017, 11:31 AM   #13
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Ain't no one gonna scold but there really isn't any need for lath when you're working over concrete slab. The thinset you spread will bond to the mud real well.
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Old 06-11-2017, 11:45 AM   #14
DanWrghtn
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Question Backing

Thanks for all the information and advice for the pan.

For the backing for the walls I'm using DUROCK for under the membrane. They have a smooth side and a rough side. Which side should face out for the membrane to go on?

Also, the edges our rounded. When the sheets are butted up against each other it will leave thin vertical/horizontal voids between the sheets. As I'm spreading the un-modified thinset for the membrane installation, do I just sort of fill these in as I spread the thinset and lay/install the membrane over? I can't imagine somehow taping over these voids first would be a good idea, but what do I know.
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Old 06-11-2017, 12:32 PM   #15
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Dan, you can use either side of your Durock, but I'd recommend the smooth side out if you're planning to use a sheet membrane for your waterproofing.

You don't want to fill any of your joints when using a sheet-type direct bonded waterproofing membrane. Just apply your bonding mortar over those tapered-edge joints and bed your membrane with a drywall knife or trowel and that joint will be fine.

And, as Davy pointed out, you do not want any metal lath anywhere in your shower construction.

My opinion; worth price charged.
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