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Old 04-01-2009, 06:35 PM   #1
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How thick to make mud bed

Using kerdi drain, shower is 30" by 60", and the drain is 10inchs off the wall. From reading the site I am going to use 5 parts sand one part portland cement, and mix it to the about the consistancy of sand castle sand (I read johns post). I was going to slope the floor .25" per foot. So the difference from the drain to the end of the shower floor will be about 1 inch higher.

Questions are:
1. Can I use play sand as the sand? Our local hardware store carries portland and play sand.

2. How thick should the pan be at the drain? i was thinking 1.5", which would be 2.5" at the wall.

3. is .25/inch the correct slope?

4. I saw a couple vidieos where somebody used one by lumber to the correct slope and put them around the perimeter of the shower. They used these to get a uniform correct slope. Once the slope is correct they pulled these pieces of wood out and filled in the gaps with mud. Would you recomend this method, or do the normal way I have seen where you just use a level around the perimeter and then slope it the best you can. I am a novice at tile work but pretty handy/knowledgeable at general home improvements.

5. how much sand and portland cement would you buy for this job?

Thanks for all your help, this has been a great site and very helpful.
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Old 04-01-2009, 06:47 PM   #2
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In the Liberry there is a deck mud calculator that will tell you how much mud you need to get. Since you are using the kerdi system pay no attention to the pre-slope part and just focus on the final mud bed. Sometimes you have to use both parts to get the right measurements to work. We need us a Kerdi deck mud calculator I guess.

I usually draw a level line around the perimeter of the shower and pack my mud to that line. In the pro hangout in the sticky "Tiricks of the Trade" someone posted a neat way to get that line using a 2x4.

I have used play sand from the box stores a lot and have had only one issue. One time the sand was wet and was a pain to mix properly. Look for dry play sand.

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Old 04-01-2009, 07:47 PM   #3
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the correct way is yes to use a piece of 1x4 wood sliced down in half and put it around the perimeter of the floor and cover the top of the drain with tape and screw the drain down into the floor scratch the floor with thin set using a quarter inch trowel then pour the mud in and use a rod from the perimeter to the drain and run it around the shower like a sqeed after you have the slope you want screw the drain back up to a suitable height for tile and thin set and let the floor dry and you are good to go and most likely it shouldn't take more than a half bag of cement to about two and a half bags of sand
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Old 04-01-2009, 09:01 PM   #4
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I'm afraid I'm going to have to disagree with our friend Terrel. I don't think he realizes that KMD is using a Kerdi drain and not a 3-piece clamping drain that he's implying. Though, I am curious as to where the liner would come into play with this method. Terrel?

KMD, assuming you can't move the location of your drain to the center of the pan, your calculations for the slope are fine. If you're more comfortable using a screed, rip some wood to 2.5" and set that up around the perimeter. I personally draw a line instead because it saves time. But can I ask if centering the drain is possible? That will keep the floor slope more symmetrical and avoid the big 1" slope over 10" you'll have between the drain and the closest wall.

Here's that link to the mud calculator Bryan was talking about. You do need to include the preslope calculations in order to account for the mud slope. According to the calculator, you need about 42# of Portland cement and 208# of sand.
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Old 04-01-2009, 09:15 PM   #5
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sorry guys just realized we live in different countries with different building codes thats how we design our shower pans
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Old 04-01-2009, 10:43 PM   #6
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Please keep in mind, terrel, that here in the "shallow end" (Advice Forum) we make every effort to keep all our advice to the visitors in compliance with industry standards and manufacturers' recommendations.

That's USA industry standards. If y'all have different standards, do feel free to discuss those in the Professionals' Hangout if you like. But when responding to questions here, please be very careful that your methods comply with US standards, eh? Thanks.

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Old 04-02-2009, 04:51 AM   #7
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The biggest problem with that drain staying where it is now is that the slope is so steep and the flange of the kerdi drain is a much shallower slope. I think it's set at the standard 1/4" per foot. I imagine you'll have a hard time getting Kerdi membrane to lay flat and not wrinkle up on the steep slope to the nearest wall, which will abruptly revert to the 1/4" slope when it hits the drain flange. If at all possible, I'd move the drain to the center and save yourself a big headache.

For the screed, I rip a 2x4 down to 1/4" widths (1/4" x 1 1/2") and nail them around the perimeter with a trim nailer (being careful not to hit a water line!). This gives me a narrow rim for my screed boards to "ride" on while I scrape the mud off. The other end of the screed board rides on the drain flange. You can remove the boards after you're finished, but I don't figure that 1/4" of wood will cause any problems, at least it never has for me.

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Old 04-02-2009, 06:40 AM   #8
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Thanks for all your helpfull hints this is very helpful.

My original plan was to use the per-sloped kerdi shower pan. Once I looked at the plumbing below the floor it would be a huge "PITA" to move the drain, all the main drain lines tie together in the area that is close to the center along with duck lines wires etc... This is why I am using the existing hole. I agree its going to be a huge slope on the 10" side, but I do not have much of a choice.

My plan is to dry fit the drain in place first to get it to the corrcect height. Once i have all my lines drawn, or my 1 * 4's ripped down to the correct height and placed around the perimiter I will place mud around the hole where the drain goes and then glue the kerdi drain to my waste pipe. I am going to have this waste pipe secured so there is no movement when I glue the drain in and also while I am making the mud pan.

I have one question still, How thick should the mud pan be below the drain? 11", 1.5", 2"? And is the .25"/foot the normal slope? I heard the one person talk about the kerdi drain being at this slope.

Thanks again for all your help.
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Old 04-02-2009, 09:12 AM   #9
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3/4" is the minimum under the flange, but you 'll find it easier if you had 1-1/4" or so to work with.

1/4" per foot is the required minimum slope. The height of the perimeter is based on the farthest wall.
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