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Randall5 10-22-2021 04:38 PM

Order of operations [mud work]
So, I am starting a new project, full bathroom remodel, and plan to do all/most of the work. I have read most of the posts on this forum and some other sources regarding mud work. I REALLY want to try to do my own mud job, start to finish. I just really find the "art" of it appealing, and as most people, I want the best possible surface and end-product. I (think) I know that it is not easy, but I am trying to approach it realistically and open minded. With that in mind, I think I have the idea about how to go about this, from start to finish, but as with many things, you don't know what you don't know. I wanted to run this sequence by the forum members to see if I am on the right path. This is for a 3'x4' shower, 3 walls, glass entry doors.

1. Assuming the subfloor is prepared properly, and the curb is in place (stacked 2x4). Walls can be just 15# tar paper, stapled floor to ceiling to joists. I could also install some form of backerboard (drywall, densshield, cbu, etc.) but it is not mandatory, correct?

2. Install 2x10 at bottom of stud cavity for liner support.

3. Pre-slope floor, using deck mud. Dry, well-packed, and sloped 1/4"/ft. to drain flange.

4. Install PVC liner. Cut around bolts, and center opening. Silicone between flange and bottom of liner. Fold corners, fold over curb. No penetrations of liner over curb or within bottom few inches of sides.

5. Next, diamond lath on walls. Ceiling to top of liner, stapled and shaped as best as possible to not protrude into the shower.

6. Mix fat mud for walls (4:1:1). Press first layer into lath, allow to setup slightly, then add thickness for float strips. Plumb, level and square strips on all walls.

7. Fill in space between strips, then screed with straightedge. Fill any gaps and re-screed. Ensure walls are perpendicular to each other.

8. Allow to setup, then score and remove the strips. Fill in the gaps, and smooth the surface with float.

9. Allow to dry overnight.

10. After the walls are done, deck mud for shower base. Use pebbles for weep holes, and set drain height. Slope 1/4"/ft. from walls to drain.

At this point, you could/should have a flat, plumb, square solid shower stall. Sounds a LOT easier in print than I expect it will be.

Couple questions:

1. When do you do the curb? Same time as the walls?

2. If you use 1/2" strips on adjacent surfaces (drywall, etc.) then the mud will protrude 1/2" from rest of wall, and the tile will add another couple 1/8"s. How to make that transition? Trim tile (pencil) or trim edging (schluter)?

3. Do you mix the mud as you go? I may/may not have a helper, and I am concerned about working time between batches. Would hate to mix too much, and have it harden while 1/2 way through a wall, and then be out of material. I would think timing of that is critical.

4. I guess the biggest question was the liner/felt transition on the walls. Felt over liner? Liner over felt? Liner over solid surface if I go that route? Then mud over liner? I have seen some detail drawings, but most assume liners are installed with CBU surface, and don't really show the assembly of a mud wall.

Anyway, that's a lot of questions, and i really appreciate any insight that can be provided.


John Bridge 10-23-2021 10:22 AM

Hi Randy, :)

6. Scratch the first coat and let it dry overnight. Then sprinkle is sparingly with water before adding the final (brown) coat. :)

Felt over the liner just for the sake of watershed. :)

Randall5 10-24-2021 03:14 PM


Thanks for the reply. I guess I was thinking I would be doing one coat, not two. The idea was to get first coat pushed into the mesh, then add more mud where the strips will go, set the strips, and then fill in the remaining areas on the wall, and then screed.

Is two coat easier for the less experienced, than a one-coat?

cx 10-24-2021 07:47 PM

Randy, I don't know if you read through the thread in the Hangout titled Mud Work Hints and Methods, but all your questions, and many that you don't yet know you have, are answered in there. If you're gonna read the whole thread, you'll prolly wanna pack a lunch, but you'll get a lot of information that's useful.

The one thing that would do you more good than any other would be to find a mud man and watch him mud a shower. It's really an area where feel is important and is difficult to describe. Seeing it done once will be a giant step in your training. Just seeing what the "mud" looks like in the wheelbarrow can make a significant difference in your progress.

One coat or two? For learning without hands-on training, the one-coat will be easier, 'specially if you won't have a helper to mix your mortar. That requires that you first install a backing material, usually drywall (not permitted in wet areas in some jurisdictions), then a cleavage membrane, then metal lath, then applying your mud. You do not fill the lath before you apply your mud screeds and set your wood screed strips. You'll get your screed strips set, then begin to fill in betweeen them and then begin striking off your excess with straight-edges riding lightly on your wood strips.

In the two-coat method, or scratch and brown method, You install no backing material. You install your cleavage membrane, usually roofing felt, directly on your open stud wall, then stretch your metal lath over that, fastened to the studs. Your first coat, the scratch coat, is to fill all the lath all around. You then scratch the still fresh mortar with a scratch rake or similar tool to create the backing for your second, or brown, coat, which will be applied similar to the one-coat.

Ain't no rocket surgery involved, but it's a completely different task from anything you've likely done before. And seeing it done once will give you at least some of the "Oh, that's what they mean" feel that doesn't always come through in the typed word very well. Don't expect to master it in one try. Your first job will be slow, it will be messy, it will feel like very hard work, it may need re-done, but it will be gratifying. There are some videos out there on the subject and I think there are even a couple linked in that Mud Work thread. If you can't find any real-life instruction, I'd recommend you at least watch a couple of those videos.

The most important thing to remember is if you wear shorts, tape the top of your boots to your legs. You will understand after your very first wall why I would suggest that. :)

My opinion; worth price charged.

Tool Guy - Kg 10-24-2021 07:55 PM


Originally Posted by cx
...tape the top of your boots to your legs.

:D :yeah: :tup2:

Davy 10-25-2021 03:37 PM

1 Attachment(s)
If you're going to make your own mud, try to find some plaster sand (sharp sand). Brick sand tends (at least in my area) to be too fine. Getting the mud right makes a big difference. I use a lot of Qwikcrete scratch and brown mud. It's pre mixed in bags, just add water. I have only found one Home Depot that has it but they say any HD can order it for you.

Here's a shower that we have scratched.

Randall5 10-26-2021 11:24 AM

Thanks for the replies, and info.

I would certainly welcome the opportunity to work with someone on an install, and will check with a few people I know. I have certainly spent several hours going through that lengthy thread, CX, and picked up a TON of information there, as well as some of the available videos. I actually think that I might make a small mock up wall in the garage and try my hand first to get some of the feel of it.

So, as for backer material, drywall, durock and/or denshield would be acceptable? Then the cleavage membrane (felt paper) and mesh. All of that would leave the finished mud layer out from the adjacent finished drywall surface. Is that defined edge finished with caulk or edging, or something of that nature?


cx 10-26-2021 12:09 PM

Mock-up is a very good idea, Randy.

You wanna determine whether your code compliance inspector will accept drywall as a backing material for your mud walls. There is a lot of misunderstanding around the use of gypsum wallboard as a backing for mortar walls in a wet area. I don't believe that was intended to be excluded when the industry banned the use of drywall as a tile backing in such areas, but I'm told there are jurisdictions where you cannot even use it behind one-coat mortar. In unincorporated areas I'm perfectly comfortable with that application.

Stapling the metal lath to CBU doesn't work well in my experience. I generally used a slap-hammer to install my lath and when I tried that as a test on a couple brands of CBU I was not too successful. One more reason to use drywall. The "special" gypsum boards, such as your DensShield, I've never tried.

You're correct that your mud wall will be proud of your backing material. I learned to cut wood strips, usually rips of about 1/2" from 3/4" boards. Those would be tacked to the wall as a stop for the mortar wall and was used as the "float strip" in that area. Leaves you with a sharp, straight edge on your new wall. This, in the days mostly before my time, was covered with a "mud cap" or "radius bullnose" or "quarter round" tile, which was a commonly available trim for Glazed Wall Tiles. They're still available, but you don't see many folks using the style of tile that they go with these days. Google up A-4200 tile and you'll see what they look like.

The alternative is to use some sort of ceramic or stone trim piece to cover the edge of the tile and mortar.

My opinion; worth price charged.

Davy 10-26-2021 05:38 PM

Cx is talking from experience when he mentioned filling his boots with mud. I watched him experience that. :D

He blamed it on the mud, saying it was mixed too wet. :)

cx 10-26-2021 05:44 PM

And it was, by Jimminy! :mad: But Little Davy was mixing and I had sense enough at the time not to tell him it was too wet.

I think Little Davy can likely bench press a VW bus. Either end. :D

Davy 10-26-2021 05:51 PM

Stiff mud is harder to work with. I think you would have successfully filled your boots regardless. But, you did good, you just kept on going. :D

cx 10-26-2021 07:09 PM

No question about that, Davy. I actually mixed my mud wetter than I'd originally been taught after that episode and it is easier to work with, so long as you don't try to get too thick on the wall. Then you get the other problem where you get the entire completed wall in your boots all at once. Only actually did that one time, though. :D

I think the one thing I took home from working with you that day was that little jump with the hawk after you scrape the mud on it, making a flatter patty before you pick it up with the trowel. Don't recall my original mud guy ever doing anything like that.

That's why I'd like to see Randy watch someone mud a wall before he even tries it himself. Little things can make a difference.

Davy 10-27-2021 08:55 AM

Yes, there's lots of little things that are left out when trying to explain something like that. That's why I mentioned the sand earlier. Having good mud makes all the difference in the world. Years ago I tried using brick sand since the brick layers had some left over. That was a mistake, most of the back wall slid down into the tub. I had to clean it all up and start over the next day with courser sand. Another lesson learned. Even the 4 to 1 to 1 may have to be fine tuned depending on the sand you have. The Qwikcrete mud I just bought is a little finer grit than they've had in the past. And sometimes I'll have my son throw in an extra shovel of sand for each bag we mix. And it just takes time to learn what the mud needs, if anything. The Qwikcrete is the best and most consistent I've used.

When you helped us that day, I believe that was a single coat mud job, which is what we were doing back then for that builder. These days I scratch all my showers from the studs. Adding a scratch coat first really helps to keep the mud on the wall, much less chance of it sliding off. The shower I'm mudding now is 10 ft tall and 5 1/2 ft wide. The back wall is close to plumb but the side walls are 1 inch out of plumb. I checked this ahead of time and was able to add a little extra scratch mud in areas so my brown coat isn't so thick. It has jambs so the added thickness won't show on the outside edge. The jambs are also out of plumb 1 inch.

Randall5 10-28-2021 08:41 PM

Well, I honestly can't see doing mud work in shorts, so here's hoping that I don't fill anything with mud (like pockets). I will look into the supply areas around me for materials options (I know there is a Daltile, but they only sell to contractors, and my contractors license expired (I am licensed in a specialty trade, but I had the GC thing for awhile too)). Other than that, there is the tile distributor that we sourced our tile from, but they are a Schluter shop, and only seem to carry thinset (TEC, I think). The local HD only has Quicrete Mortar Mix and Mason Mix. I will keep looking.

Am I crazy for thinking I can do this, first time? I know most people seem to go towards the Kerdi/Wedi/Hydroban/Redgard direction, and that has it's own pros/cons (walls out of plumb, surface not flat, etc.). I am hoping that a little thought, time, effort can produce the desired result, which is solid, waterproof flat surface.

cx 10-28-2021 10:04 PM

A geographic location in your User Profile is frequently helpful, Randy.

I've tried both the Quikrete Mortar Mix and Mason's Mix as fat mud and found both wanting. While they'll do OK for mudding a curb, they didn't do well on walls for me. Can't say exactly what was missing. Perhaps operator talent? :)

And you're certainly correct that for flat and plumb, you just can't beat mud walls. And for those that do it on a regular basis, it's also fast and cheap. For those of us who did it occasionally, strike out that fast part.

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