Shower Mud Bed Tear Out?

[Kman]

I've (almost) always had to work by myself, and finding shortcuts to get through some of the more labor-intensive parts was a given.

When doing a mud floor with Kerdi over it, I'd rip the edge off a 2x to about 3/16" or so, and make enough rips at the appropriate lengths that I could wrap the perimeter of the shower walls. I'd set the top edge of them at the height of the mud bed at the walls, and stick them to the wall with an 18-gauge trim nailer into the studs. This gave me a screed edge at the perimeter that I knew was at the correct height all the way around.

No need to pull them out, since they're really thin and they're covered with Kerdi anyway. Your curb may not be tall enough to put them up, but you can try it and see.

Once they're up, you have a good visual to work from. You'll want to put the mud in much higher than the screed points, pack it down good, and then use your straight edges to scrape off the excess above the rips and the drain flange.

If you don't have a wood float, get yourself one. Use it for the initial packing in of the mud. Keep it oriented from wall to drain at all times. Turning it perpendicular, particularly while packing in the mud, will result in divots in the mud.

You really have to work quickly, as mentioned before. One tip that might help is to start on one corner or one end of the shower and get it in "decent" shape, i.e. packed in and scraped off. It doesn't have to look pretty at this point. Then start the next batch going clockwise around the drain. For the next batch, go the other direction. Keep alternating until you're finished. This keeps the edge of the mud where you started from getting too dry if you were to work all the way around in the same direction. (Hope that all makes sense.)

[Davy]

I use different lengths of lattice sticks like John. And as Kevin mentioned, it's important to keep the lattice (or whatever you use) pointed towards the drain at all times as you cut the mud. Another thing to watch, make sure your mud has pitch all the way to the walls. It's easy to let the corners flatten out.

The picture below has a notch to allow for tile thickness. You won't need that with a Kerdi drain.

[Flintluck]

Thank you all for the advice! It was very helpful. I installed this evening using a 5-1 mix split into 3 buckets 60lb each with a little under 10 cups of water per batch. I did the full 3x5 in significantly less time this pass though not 45 min and was able to pack and screed well. I also didn’t feel like it was drying out as much as last time and I was using less water as well. This one was definitely packed a lot better too.

I’m cautiously optimistic.

I’ll let you know how it’s looking tomorrow. Also, should I cover the pan with plastic to help it cure? I’ve seen that mentioned several times.

[cx]

Yes, cover the new mortar with polyethylene sheeting for as long as possible.

My opinion; worth price charged.

[Davy]

If you don't have a roll of poly laying around, grab a couple trash bags.

[cx]

Or Mrs. Jonathan's favorite shower curtain.

[Flintluck]

Okay, great. I’ve had it covered since I finished last night. The plastic has condensation all along the bottom. I looked at the bed earlier and the slower drying and better, quicker packing makes me pretty optimistic this one’s going to do the trick!

Should I leave the pan covered a couple more days?

[Kman]

I would leave it until you're ready to resume working on the shower. The first week to ten days would be sufficient.

[Flintluck]

Well, I kept it covered about 4 days from when I finished the pan. I removed the plastic sheet last night as we want to get this waterproofed and tiled this weekend. You can tell the middle area is a little darker as the edges did dry more quickly under the sheet, and most of the condensation fell back into the middle. The bed seems to be a lot more consistent and uniform though the 5-1 mix is definitely more porous and rougher than the 4-1 Mapei I previously used.

I swept and vacuumed the excess off the top, which wasn't a whole lot. I walked on the bed and didn't feel anything crumble or move under me. Given the mix, I think I could definitely dig out parts of the top in certain areas, but I'm not sure that's an appropriate test. I figure if there are any low spots after I do one more pass with brushing and vacuuming, I could fix those with a thin-set and move to waterproofing.

Is there anything I need to check to make sure the pan is good before moving on? I've attached an updated photo of the pan.

[cx]

Get the Kerdi (I'm assuming since you have a Schluter drain) installed, Jonathan. Works the same as covering with poly sheeting, only better.

Originally Posted by Jonathan

but I'm not sure that's an appropriate test.

It's not. You'll be able to do that when you tear out that shower in 50 years or so.

My opinion; worth price charged.