Hi Everyone,
I'm new here, and found this board while researching information on building my own tile shower. So far, it's been a GREAT resource, and I've learned a ton, so a big THANK YOU to start!

I'm a big DIYer and my wife and I bought a house, and spent the past 1.5 years pretty much gutting everything, and redoing floors, walls, ceilings, electrical, plumbing, cabinetry, etc... all myself, so I generally know my way around the home. During this renovation, I've gotten pretty decent with tile as well, after laying a few floors, and am now building a tile shower in the master bath.

I've got all the plumbing done, and will be finishing up the framing this week (I hope... as I do all this in my "spare" time, after work, and college).

I stumbled across the wonderful article by Harry Dunbar (here: http://www.ontariotile.com/preslope.html ) on building the shower pan, and I have a few questions though, that I thought I should get clarification on, before I actually get to the point of doing it.

1) For the "Mortar-Mix" used in the pre-sloping under-liner slab, a latex additive is used for strength. Is there any specific latex additive to use for this? Am not seeing anything specifically made for concrete at the big box stores, so am I missing something? What would be a suitable product to use for the additive, that is readily accessible at such stores?

2) The consistency of the Mortar-Mix for constructing the above mentioned slab. It looks a little wetter than the "deck-mud" discussed later in the article (for the top mortar bed). Is it? What type of consistency should I be shooting for with the Mortar-Mix? Do you add latex additive only? Or latex additive with the water? What type of ratio should be added in terms of latex/water(if any) to the mix?

3) Being that I've never done a shower pan, I have no idea how much portland cement and sand I'm going to need?!?! My shower is going to be about 36" wide, by about 60" long. How many pounds (or bags) of cement/sand am I going to need for the mortar bed, and the tiling slab for a shower this size (obviously at a 4:1 ratio)?

Thanks in advance for the replies, as well as the wealth of information I've already found here!

You can find latex additive in the tile department at Lowe's and Home Depot. I've never found the need to use it, particularly when working over a concrete slab. But it certainly doesn't hurt to use it.

I know a lot of the guys buy some portland and sand and mix it themselves. I find it easier to buy sand topping mix in a bag at Lowe's. It's a little heavier in portland than what most like to use, so you can add a shovel or two of sand to each bag. There's no magic number for how much water to add, you have to add a little at a time until it's the right consistency. You should be able to ball it up in your hand, and it should stay that way with very little moisture in your hand.

If you decide to go with the sand topping mix, you could probably use about six 60lb. bags. I always buy extra, because you can always take it back. But it's very difficult to have a good finished product if you have to stop in the middle of the job and go to the store for more materials.

Kerelastic by mapei is a good latex additive. Personally I use about 40% latex 60 water. I find that straight latex mortar sets up too fast. it's not an exact science with the mix consistency and ratios. make sure you pack the mortar bed well by beating it with a scrap of wood or a float, then scrape flat.

Thanks for the info guys. Good to know on the latex additive.

Kman,
Just to be clear, I saw that that's the consistency described for the upper "tiling slab," but should I be using that same consistency for the lower pre-sloped slab under the liner? Does it just not matter all that much, as long as it's a workable consistency, because it'll dry the same either way?

Thanks again!

They should be the same.

Consistency does matter. The water to cement ratio effects the cured strength of the mortar. Too much water during mixing makes for a weaker mortar. if it's too dry for the chemical hydration of concrete to proceed then it will end up crumbling. stick with the snowball consistency, or fairly close to it.

Thanks for all the info so far guys. I need a little advice now though.

Throughout the past week, I finished all of my plumbing, reinforced the floor, framed out the shower, and started my shower pan according to the page I referenced earlier. I put my liner down, laid my lath, attached my drain flange, and things were going great. Then I got to the pre-sloped lower slab... and the nightmare began. As I said before, I have gutted and rebuilt and remodeled my entire house, but this lower slab may be the worst project I've done yet... not because it should be difficult or anything, but somehow that's how it worked out. Allow me to explain.

I mixed together the dry components and started adding the latex and stirring. I don't have a nice big wheelbarrow at my house, so I bought one of those big mixing bins they sell at the big box stores, which are CLAIMED to be made for mixing this stuff. Sure enough, a couple minutes into it, and the entire bin starts shattering and breaking apart. Great, so now I've lost a bunch of my mix, which is so conveniently on my cement driveway. Oh, and even better, it's now started raining. In retrospect, I should've just called it quits here, and started again another day, but my pride, my dollars, and the amount of work I've been putting into this project convinced me that I should continue. So at this point, because I've lost a bunch of my mix, I start adding more components so I'll have enough. I'm in a hurry because of the rain, so I mix it, and start to throw it in buckets to haul up to the shower. After dumping the mix onto the lath, and trying to manipulate it, I realize it's not quite right. It doesn't want to spread easily, and screeding is almost impossible. It almost seems like it forms a very thin sheen layer at the top, that when I try to use a screed on it, it the surface tension pulls at the dryer stuff underneath, pulling clumps. Obviously at this point, there's not way that I can get this mix back out. So instead, I patiently work at packing it, and manipulating it for the next hour or so, until it forms a nice slope the whole way around, all going to the drain. About 45 minutes after I'm done, I check on it, and it's the sheen layer on top of it is there, and it's got a little bit of moisture on it in a few spots. By this morning, the whole thing is dry.

The problem is that now I'm concerned about this under-layer. Because of how the project went, I'm betting the mix is not perfect (and neither was the consistency). It really seems like it's too strong on the portland cement side. It has dried though, and the slope still seems pretty good.

My biggest question and concern, is wondering if this is going to be a problem!?!? Extra portland cement would actually STRENGTHEN the under layer if anything, right?! Are there going to be any problems leaving this layer as is and proceeding with the project from here? Obviously I'm infuriated with the POS bin that started all of this, and for my top layer, I'm going to be getting a nice wheelbarrow. But right now, I just want to make sure that this isn't going to ruin the shower in the future, or affect anything else, by using the lower-layer I already set.

Your advice and expertise is greatly appreciated. Thanks!

Let's back up for a minute. Do I understand correctly that you put the liner on the subfloor, then started with the mud floor? Hopefully you're what you're calling a liner is actually a cleavage membrane that serves to keep the subfloor from drawing moisture out of the mud.

If that's the case, let's move on to what you have so far. If the mud you put in was packed in well, feels solid and is not cracking, and has a decent slope to the drain, it should be fine. It most likely got too wet to work with and that caused the problem. More portland is not necessary. It will only cause the mud to shrink as it dries. Stay with the recommended recipe for deck mud.

Unfortunately your mix ended up too wet. There should be no sheen on the deck mud as your packing or screeding. It may either shrink or crack in a day or two.
What did you end up using exactly, for the mixing components?

Although a latex additive will add some extra bonding strength to the mix it's not necessarily needed. For a DIY'er its a challenge to get the consistency right using latex additives.

You may be ok with the first preslope mix as long as there are no cracks or excessive shrinkage.

As Kman pointed out, a clarification on the liner placement would be good before you continue on. Hopefully you meant tar paper, then lath.

Thanks for the responses guys.

First and foremost, I guess I shouldn't have referred to it as "liner." Let me clarify. What I laid down was actually a layer of plastic sheeting (like a plastic drop cloth), and put lath on top of it, just to act as a separating layer between the lower deck, and the subfloor. I did NOT put down my actual moisture barrier shower liner yet, as obviously that goes on top of this layer. It would serve no good to go UNDER this first layer!

I guess the general consensus on my lower concrete deck then, is that I should watch it for a few days to make sure it doesn't crack or shrink, and if it doesn't I'm probably okay. The deck was dried the morning after I laid it, and by now it's been almost 2 days, and it still hasn't really shrunk or cracked. How long should I wait to see if it does to know if I'm safe or not?

Thanks again for all of your help.

If it hasn't done it by now then your probably ok to continue on.



Your absolutely right, but you would not believe how many are actually done that way.
We just want to make sure, so you don't end up creating a big problem down the road.

It obviously depends on available space, but when I did my shower pan, I brought the cement and sand bags upstairs and mixed everything right next to the future shower. Oh, and no problems using a black mixing tray from HD, it survided 3 or 4 mixes no problem.

just doing the same job as you are right now, for the first time. Basically just followed the steps in the site you mentioned and so far its been going ok. just put down my membrane tonight over the first sloped layer of mortar, found it awkward around the kirb to get it looking properly but after a while it looks ok, I think i will leave it overnight then fill the membrane with water, just to check for leaks around the drain before putting in my top coat of mortar. good luck with your project