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03-14-2006, 10:23 AM
Hello everyone
I am new to this board. I am currently getting ready to do the shower pan for a 4'x5' tiled shower. I was wondering for the first sloped layer of mortar (after putting down 15lb roofing felt and lath stapled), can I use the premixed "mortar mix" being sold at the local Home Depot or should I mix my own. I understand the ratio is 4:1 with 4 parts sand and one part portland cement. I also understand reading the posts that I should use a "latex additive" as opposed to water to make the "mud". What brand and where in Home Depot do I find this additive? I was looking around the store last night and did not see any near where the mortar mix bags were. I did see some type of additive near the tile section. Any help would be appreciated. :yummy:

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03-14-2006, 10:29 AM
Welcome, Den. If that be your front name. :)

Go to our whorl-famous (Liberry). Find the Shower Construction thread. Find post number 9. Read.

Gonna tell you just what to mix. You want about 5 to 1 or even 6 to 1 sand to Portland mix. No addatives; only water. And very little water. Just enough to make a ball and have it stay together. Sand-castle consistancy.

My opinion; worth price charged.

03-14-2006, 12:10 PM
Den (?)

I took the route of the pre-mix mortar from Home Depot. It was a Type-S mortar mix. The Type-S is quite strong. I used it for the pre-slope under the PVC liner and I also used it above the liner as my final bed. In retrospect I would have done the final bed with the dry-pack recommended on this site. But I didn't find this site before I set the bed. Oh well.

So in my opinion, go for the pre-mix for the pre-slope. You'll only use about 1/4 of a bag. Let it set and install the PVC (or CPE) liner. Then use Portland cement and sand for the dry-pack bed.

Being an engineer I like to know the "why" behind the dry-pack. So far I've deduced that it's easier to work with than a typical mortar mix and it passes water better. I keep hoping the pro's here will shed more light on the reason for dry-pack instead of a stiff mortar bed.


Kirk Grodske
03-14-2006, 12:21 PM

Dry pack doesn't shrink and then cause cracks in your tile job. It is also easier to shape to a perscribed and accurate slope. It is the right thing to use.

In the Liberry, there are the only two options to use, IF you are going to do it right!


03-14-2006, 12:34 PM
The Mortar Mix contains lime, Jason, the purpose of which is to make the mix sticky. For screeding mud beds, sticky is the last thing a fella wants, which is why we also don't recommend the use of latex addatives in lieu of water in the dry-pack.

The Portland/sand dry-pack mix will be easier to work, have a higher compressive strength, and shrink less than the type S mortar mixed per instructions. And the dry-pack is more pourous for the final mud bed, which is not really an important point in the pre-slope as you indicate.

The mortar will probably work all right in the pre-slope, but it has no advantage there at all. The Sand Toping comes pre-mixed in bags, too, and all you need to add is a little sand and water.

My opinion; worth price charged.

Kirk Grodske
03-14-2006, 01:11 PM
CX said it better than me. Kirk

03-14-2006, 01:23 PM
Thanks to everyone for the replies to my post. I found info in the "Liberry" on the ingredients for the deck mud. It seems that Quikrete "sand topping mix" and "all purpose sand" was recommended by davem. The ratio was either 4:1 or 5:1 (sand topping mix to sand). Water instead of latex additive was used.


03-14-2006, 09:34 PM
Does the latex additive in the dry pack give you any special benefits? In a small shower, 36x36 drain in center, what would be the best method to pack the mix and when do I know the mix is finished packing? Do you pack around the drain/pea gravel or is that left sort of "unpacked"? What are the most common errors with first time dry pack users?

Sorry but I hate to do things twice.


03-14-2006, 09:57 PM
The ratio was either 4:1 or 5:1 (sand topping mix to sand)

Actually, the ratio is 4-1 or 5-1 of sand to PORTLAND CEMENT. (4 or 5 parts sand to one part cement) The prebagged Sakrete stuff is generally 3-1, so you just want to add a third of a bag of sand (or so) to a bag of Sand Mix.

Brian, no, forget the latex. You do have to pack the entire floor, including around the drain, otherwise it'll crumble on you the next day. You don't have to compress it with steamroller force, just give it some light muscle with a wood float. Most common error is too much water , I believe. It just doesnt seem like the stuff will get solid because it feels so dry, but it will. Remember, just add enough so when you squeeze a handful together, it stays that way.

03-14-2006, 10:45 PM
I've done 3 dry pack mortar beds now, and it wasn't till the 3rd time that I got it right. The mortar has to be DRY. While you make it, if you think it's too dry, then stop adding water. Only with it dry like this can you make perimeter screeds. Also, if it's too wet, when you use a straight edge to scrape excess mortar off, all the mortar will stick to your straight edge.

I think the Schluter folks have an excellent clip on what the mud should look like.

03-15-2006, 12:05 AM
Mmmmm. Efren? How's come you done did three mortar beds when we know you ain't done but one shower? :D

03-15-2006, 05:53 AM
Easy! he did all three in the one shower! :yeah:

03-15-2006, 07:12 AM
I noticed alot of reference to the word screed. Forgive me I am a newbie. What does it mean in relation to mortar beds?

03-15-2006, 08:24 AM
To flatten and slope.

03-15-2006, 08:39 AM
Unfortunately, it's one more of the words used several different ways in the industry, Den.

1. A screed is a long straight edge of some sort used to "pull" the surface of the mud or concrete to scrape it flat.

2. A screed is a board or other straight material set on, or attached to a floor or wall, or embeded into the mud on a floor or wall for the purpose of guiding the "screed" in number 1.

3. A screed is a pile of deck mud or a long strip of deck mud that is set in place and leveled to act as the "screed" in number 2 above. Sometimes referred to as a grade screed or grade pile.

4. Screed is sometimes used to refer to the deck or wall mud material itself.

There are probably other uses that I'm overlooking, but in general the term has something to do with causing mud to be flat and "on plane."

My opinion; worth price charged.

03-15-2006, 08:57 AM
cx, not sure if you remember, but I screwed up really bad my first time and tore everything out. That's 1. Then, I decided to switch to kerdi and tore everything out again. That's 2 and 3.
See my old thread. It's a prime example of what NOT to do. :shake:

03-15-2006, 09:01 AM
I remember it well, Efren. :D

That's why I posted. :stick:

03-15-2006, 02:04 PM
My god, efran, I just read your first experience with your shower! I hope everything turned out ok. CX, we newbies are very lucky having someone like you and others who helped efran out with his project. :clap1: You deserve the huge salary you receive working as moderator (wink, wink)

03-15-2006, 03:15 PM
Naaaa, the real credit goes to Mrs. Efren for staying on the boy's butt and makin' him do it right. :D

03-16-2006, 10:04 AM
The Mrs. is pretty scary when she's mad. :devil: