Dry pack mortar question: shower pain

[cx]

Yes, clearly confusing, Jake.

You need also to note the "Project Tip" just below bullet point number 6.

They're apparently trying to tell you (with no clarity at all) how to tile over a "fresh mortar bed" without using thinset mortar. At least that's the only thing I can guess from that.

While I hesitate to tell you to deviate from product manufacturer's instructions (see my warranty information below), I suggest you disregard that number 6 all together. You will be setting your tiles using thinset mortar "over a cured mortar bed," and the tile industry standards call for a cure time of a minimum of 20 hours, but suggest longer cure time may be preferred, "up to 10 days."

I suggest you not use that mix straight out of the bag, but that you temper it with more sand, and that you wait at least the full 20 hours with it covered with polyethylene sheeting, or similar, and that you tile it any time thereafter.

My opinion; worth price charged.

[Jake20]

Thanks for the advice.

Substantial difference in the shower floor: I added sand to the mortar mix as advised; much smoother surface and easier to work with. I also took your advice and covered it with plastic after spraying some water on top. Checked it this morning and very sound. Sprayed some more h20 and covered it again.

[cx]

Don't really wanna add water, Jake, just preserve what's already in the mix. It's plenty. Spraying water on your deck mud risks washing the Portland off the sand grains on the surface.

My opinion; worth price charged.

[jadnashua]

Concrete curing is a chemical process. Adding water risks problems CX indicated. The plastic over top helps to preserve water that is needed for the chemical reaction and is useful when the humidity level is low and if it's warmer as that can lead to more evaporation prior to the chemical reaction from completing. Adding some after it's started to cure won't hurt (maybe the next day), but right after placing, it could.

[Jake20]

Thank you for the replies, all very helpful.

A little off topic but it’s part of the same project so I’ll keep it here. I made a complete rookie mistake. I finished the top mortar bed before applying lath to the shower curb, so it’s not secured from the inside of the shower. My fear was that the lath would damage the liner so I figured securing it to the outside of the curb would suffice. Now I know why people nail through the inside surface of the curb, something I was tempted to do. Can this be fixed? Thank you.

[ss3964spd]

Thanks for keeping your questions regarding this project in this thread, Jake.

You really do need the lath on the shower side of the curb secured by the mud bed, I can't think of any other way to do it. To that end you'll need to remove the mud next to the curb enough that you can get the lath in there, then re-fill the gap. Whatever mix you are going to use to form the curb over the lath can also be used to fill the area you excavated, just be sure to pack it well. I'd probably go an inch wide and as close to the liner as is comfortable. Less than an inch wide I think you'll have trouble packing it.

[Jake20]

Appreciate it, Dan. I was afraid of that. The only other solution, and I’m a rookie so this may be totally outlandish, was maybe securing some sort of bracket (an upside down “U” shape) to the outer portion of the curb so that it passes over the top and holds the inner section of the lath fast.

[Jake20]

I wound up removing the top 2 2x4’s from the shower curb, peeled the liner back a little, and was able to get the lath where it needed to be. As suggested I excavated a small area of mortar near the curb, and will fill in with fat mud as I float the curb. Any fat mud suggestions?

[cx]

Jake, if you'll look in the Shower Construction thread in our Liberry, you'll find information on the various mortar mixes you need for a shower, including the "fat mud" you'll want for your curb.

My opinion; worth price charged.

[Jake20]

Sorry about that. Yes, lots of good info. Found what I was looking for.

[Jake20]

I appreciate the advice with the shower curb issue; worked like a charm.

Moving forward, I have a few imperfections in the 2nd mortar bed, unrelated to the curb, which need filling in. I’ve read that I can do this with thinset. Do I make the repair, allow the mortar to dry, and then proceed with laying the tile? Or, do I repair and immediately lay tile, prior to letting it dry? Does it make a difference?

[ss3964spd]

Using thinset mortar to fill imperfections in the mud bed is doable, Jake, so long as the areas to fill are not too deep or large in diameter. Filling them at the same time as you set the tile is also doable, you'll just need to take care that you don't rake out the fill with the trowel while combing out the mortar to set the tile, and that you don't bed the tile in the fill area deeper than the surrounding tile.

Otherwise, fill the spots, let the mortar cure, then go back and set your tile.

[Davy]

I find it handy to vacuum the mud before trying to fill voids or tile it. You want all the crumbs picked up. If the mud is too rough to patch or tile, rub it down lightly with a rub stone or even a block of wood with course sand paper before vacuuming. Just make sure you get any humps or divots taken care of before tiling. The tiles will want to follow any imperfections that are left in the mud, especially when using small tiles.

[Jake20]

Thank you.

[Jake20]

Ok, so was considering the thinset repair, as above, until I vacuumed the floor and large chunks of mortar came off. Most of the floor is very sound and without defect, had no issues running the vacuum over those. Clearly I cannot repair the above with thinset.

I removed the fragmented pieces down to the liner. Can I just pack those areas with sand topping mix or do the repairs require something more involved?