To create a shower floor from scratch we use what is commonly referred to as “dry pack mortar” or deck mud. Deck mud contains three ingredients: regular portland cement, sand, and water. That’s it. Don’t let anyone tell you that a latex additive or anything else is necessary. It is not. Properly mixing and installing deck mud will create a shower floor that will last for years and years.
The ratio is very important to achieve the correct consistency and stability. You want 5 parts sand to 1 part cement. Your ratio can vary from 4 to 6 : 1 but the 5 : 1 is what I use and find to be the easiest to work. You want just enough water to dampen the mixture. It’s not a lot. Too much water will cause your mud to shrink as it cures and compromise the stability of your base. You just want it damp – really.
The easiest and most convenient way to get your mixture correct is to buy the quikrete “sand and topping” mix which is sold at all the big home centers. This is already mixed at a 3 : 1 ratio. For a 60lb. bag you need only add 30lbs. of sand to it. This is how I mix mine – it’s convenient. The easiest way to mix it is with a regular shovel or garden hoe in a mixing box or regular wheelbarrow, although you can mix it with and in anything that works for you.
After it’s mixed it should just be damp. When you pick up a handful of it you should be able to squeeze it without water dripping from it. It should be able to hold it’s shape when you squeeze it, just like a snowball.
Whether you mix the entire batch from scratch or use the sand and topping mix it should all have this same consistency. If it is any wetter it will shrink as it dries and it will not be as solid and stable as it should be. I usually start with about 1/2 gallon of water and work up from there. I think. I really can’t tell you exactly how much water to use because I don’t measure it. I’ll have to do that and include it here.
As you install and shape your base, slopes, and shower floors you want to pound the mix with a wooden or magnesium float. I mean beat the hell out of it. You want the mud packed very well with no voids. The harder you pack it the more stable it will be. I have or will have individual posts to instruct you how to shape shower floors, etc. This one is strictly to describe the proper recipe for your mix.
A couple of companies also make a mix specifically for shower floors and mud beds. I’ve only used one and it worked quite well. Just follow the mixing instructions on the bag and start with the minimum amount of water they suggest and work up from there.
When set (about 24 hours) the mud bed will be a perfectly suitable substrate for your tile installation. It will be sandy on the top. You can scratch it with your fingernail – stop doing that! It’s normal. I understand it’s counter-intuitive, but it really is normal.
Although you may have been led to believe that creating a shower floor from scratch is a very difficult thing to do, it is not. With careful planning and attention to detail you can create a shower that will last for years without any problems. Getting your mud mix correct is at the core of the proper method.
This blog is a treasure trove of information.
Hey Roger, loving your page, lots of great and concise info! When doing a large mud bed, how do you treat cold joints? Or does it even matter? Thanks man!
Hi Andrew,
With properly mixed deck mud cold joints aren’t normally an issue. That said, when I begin a new pack next to a cured, I always put a mortar slurry between the two. While the deck mud itself will compensate for movement within the bed, I cannot control the substrate beneath – especially with a bonded bed. The thicker the mud bed the less of an issue this is.
Roger. The last two tile jobs I finished with your help and I want to thank you. Its hard to find quality and solid information online because you have to deal with all the kooks and ignorant people that post videos and blogs when they dont know their rectums from a hole in the ground.
That being said, I have a guy wanting me to use dry pack on 3200 sq ft of floor that is going to have 30×30 porcelain tile set on top. He refuses to purchase any underlayment I suggest. Ive done shower pans before but nothing this size. I know ( I think) that it has to go in on top of thin set to adhere to the existing concrete floor. It is cured concrete. The area is a dining room and it will have alot of foot traffic. I just dont want it to crack in a couple years or after another So Cal earthquake.. Whats your always dead on advice ?
P.S. Thank you for your service.
Hey John,
Provided the bed is over 1″ (technically over 1 1/2″) it does not need to be bonded to the concrete. It’s actually better that it is not, it gives better uncoupling properties. The concrete can move and crack all it wants without affecting the tile.
Mud beds for full floor tiles are different than mudbeds for shower floors.
Thanks for the quick response Roger. To get knowledge from a Master Tiler free of charge is like gold. What you share requires years of hands on experience and most Journeymen hold their skills close to the vest and share nothing. And if I didnt mention it..Thank You for your service to our country..
Ps.. I sent a more detailed email with further questions at the same time I posted this.
I have a similar situation in our commercial building converted to a house:
– ~4500 sq ft of uneven concrete slab
– From one end to the other (~100’) it drops ~4”
– Have found a mud bed is the best option
Questions:
– From slab to mortar bed to thinset to tile, but where/how should I put a waterproofing layer?
– What material should waterproofing layer be? FYI, I don’t think they waterproofed well under the concrete slab.
– Anything else? Do you have a website or Youtube channel?.
PS, forgot to mention I’m in Florida. Also, can you recommend a sand type? I figured I’d just have a load delivered.
Hi Sandra,
First question I have is why do you want it waterproofed? There is no real reason to waterproof it unless it’s inside a shower or some commercial application.
I do not have a youtube channel, I don’t do videos because I sound like I’m gargling marbles when I talk. And you posted this question on my website.:D
Sharp sand is best (If you have it delivered they’ll know what that is), if you can’t get it regular sand is just fine.
You said mud for the shoeer floor is different than deck mud. I am guessing that deck mud over concrete would need to be a bit wetter than the shower pan mud because the slab is going to suck up some of the moisture?
I meant the application (the requirement to be waterproof) was different. There are subtle differences such as the bonded vs. unbonded, etc., but the mud itself is identical. If going over concrete it should be saturated before the mud is placed over it so it doesn’t suck moisture from the mud mix.
Thanks Roger for clarifying. I am purchasing all of your books. I know your experience and willingness to share it have saved me hours of time and put me on the fast track to journeyman. I have watched videos of men in other countrys mix their mud and set lft with little more than sticks and shovels. This inspired me but your wisdom gave me the confidence to go ahead and give it a shot.I am documenting this job so I can share with all and encourage others to go for it. I also have love and respect for those that served and are serving our country. Its not much but purchasing your books and the donations you make through these purchases is a selfless act we can all get behind.
So a cured concrete floor needs to be clean and free of contaminates and dry. The large format tile can be set on the dry pack or deck mud securely so the sand can absorb movement from the slab beneath it and the tile will not be affected. I am not applying thin set beneath the dry pack. I am using fat mud to set my screed sticks. The mix will be almost identical in sand and cement ratio but lime and more water will be added. I will also have some cement to sprinkle on the base of the screed sticks to have them firm up and keep their shape. The dry pack will surround these and all will bond together to make a firm and flat foundation for setting the 30×30 porcelain tile which I will set with lft mortar making sure to back butter each piece for what I hope to be 95% or better coverage. Have I missed anything ?
It sounds like you got it all.
Now the hard part…putting that into practice.
I used a laser level to mark my floor height. I took into consideration the width of my tile which is 3/8 and another 1/8 for thinset. Now Im finding that the deck mud I will need drops down to 0 in some places along the floor. Do I need to grind down the slab? Or something else when it happens in the middle of the floor. The heighth I leveled from was the existing walkway outside of the entry doors at threshold.
Unless you want to grind it down 3/4″ you need to raise the height of the floor so there is a MINIMUM of 3/4″ of deck mud everywhere. You can’t go thinner than that with deck mud.
I was planning on using the deck mud for the shower floor then installing then tiling the walls, then installing the tile on the floor. My concern would be that if a fingernail could scratch the mud would it be bad to walk all over the floor for several days while I’m installing the walls or is that not a problem?
I do it all the time. Just put down some cardboard
James is correct, just throw down some cardboard.
I’m still trying to figure out the benefit or reason not to add the manufacturer recommended latex “ad mix” to deck mud. While I’ve heard people say that ordinary 5:1 deck mud can develop compressive strength of 3000 lbs per inch, and will make a shower pan that will last for years, my understanding is latex helps resist the mud breaking down due to flexing and holds it together better. Couldn’t that contribute to a more durable longer lasting shower pan? Besides the extra cost and possible superstition of adding the latex, are there any known downsides to workability or durability?
Hi Paul,
The reason they ‘recommend it’ is because they want to sell it. The manufacturer of admixes are the only ones who recommend it.
It is advantageous in some applications. Where you NEED flexibility, like an inadequately framed substrate, in certain climates, etc. But ALL of those have better solutions and in some, such as the framing, require different solutions. You should NEVER have a mud bed anywhere that requires ‘flexibility’. There are other, better solutions for any argument they make.
As a side note: the reason you add so much sand is to achieve ‘flexibility’, although not in the manner it’s normally used. Because of the amount of sand, the mud bed can shift to a point without transferring that movement up through the tile and grout. It can move without affecting your tile. That is flexibility, in a tile context.
Workability-wise, it makes your mud more sticky when you’re trying to form it. Which is NOT a good thing in this application. Regular deck mud without admix works just fine.
Hi Roger
Using the quickrete sand and toping mix method with the added sand that you mentioned. Should I use the Quickrete play sand (good and dry) or the regular Quickrete sand?
Thanks
Robert
Hi Robert,
I prefer the regular quikrete sand, but either one works fine.
Thanks Roger, it worked great!!! Thanks for the great advise.
Thanks for both the question and answer on Sakrete mix! Just getting back to a long idled project and getting to that stage, so two people helped out.
Terrific site & terrific tutorials that are excellent across the board.
A tip o’ the hat.
Hey Roger.
I had my first attempt at pre sloping my shower pan (layer underneath liner). I purchased quikrete sand topping mix. I mixed it accordingly to proper consistency and applied thin set beforehand. When I threw it down and started packing I noticed that I had quite a bit of pebbles in my mix. It made it more difficult to get a good surface packed on top. The following weekend I came back and noticed the spots around the pebbles were crumbling pretty easy. I took out the soft spots and attempted to patch it with same mixture, only this time I tried to use a sifter to get the pebbles out. Unfortunately the patch job crumbled as well. Now I have a pre slope to half cured good and half bad. Any tips you can give me? I’m open to making the mix a different way without using that sand topping mix.
Thank you in advance!
Hi Justin,
You can spray the entire pan with water (from a spray bottle, don’t blast it with a fire hose) and cover it with plastic for a day. This will reactivate the cement crystallization process and allow those soft spots to cure.
Are you familiar with the Sakrete Sand Mix? This product is available in my area and I am wondering if it requires additional sand to achieve the desired 5:1 sand to cement ratio?
Hi Brian,
Sorry for the delay, got lost in the shuffle somewhere. I’ll answer for future reference for others, though.
The Sakrete sand mix is a 4:1 ratio. You can use it as it or, if you desire 5:1 (I do), you can add 12 lbs. sand to each 60 lb. bag.
Thank you for posting this info.
Hi, we used custom float bedding mortar to make the 2 layers (both layers sloped PVC liner in between) for our shower pan what I need to know is should I put redgard over the top of the shower pan before laying tile or does the tile go directly on the mortar?
No. The membrane under the deck takes any water down the drain.
He’s right you know.
Thank you that’s what I thought but I wanted to be sure since the last 2 times this shower pan was done by professionals it leaked alot!!. So we decided to do it ourselves and I want to be sure that the third time is the last!!
If it leaked it wasn’t done by ‘professionals’, regardless of what they called themselves.
Hi Linda,
Tile goes directly to the mud (mortar). Do not use redgard over it, you can trap moisture between the waterproofing layer which will lead to issues.
I followed your guidelines and constructed a mud base; it came our just as planned (your instructions were great, especially the “hammer” line 3 1/2″ above the base perimeter). My question is: how smooth does the pan surface have to be? Even after honing it down with a brick, it has some davits and such. Should I be concerned or will the thinset be sufficient to fill the voids so that the Kerdi membrane will lay relatively flat ? I know that you are not clairvoyant and don’t know how deep the davits are, but in general, can the surface be ( for example) as rough as brushed concrete or does it have to be as smooth as a polished patio surface ? I was thinking that maybe I should lay a mortar layer over the pan to get the surface smoother, but I don’t know if that is overkill or if it will even adhere to the already-dried base.
Thanks.
David
Hi David,
Rough is just fine. Thinset will fill quite a few blemishes. It doesn’t need to be smooth by any means.
Thanks very much for all of your help.
Because I was afraid that I would accidentally bump and even damage
the membrane on the Kerdi drain during the pour, I cut out a 1″ thick circular piece of plywood and used the floor cutout hole as the anchor in the drain hole to simulate the drain while I formed the mud base. Since I have access under the shower, I additionally cut a 2″ drain hole in a piece of plywood, beveled the edges, and screwed it to the underside of the shower floor so that when I set the drain, it would be at the correct height, and the supporting mud would not fall through the hole, but would stay compacted around the bowl of the drain. Since the site cannot support the photos I will try and send them separately. Just FYI, the shower is 4-1/2′ x 5′ and is curbless.
Again, Mahalo. for your help.
David
Sorry, I tried to send photos separately but the site won’t support them; however, if any readers are interested in photos of the simulated drain and the beveled drain support under the floor, if they leave their email address, I would be happy to send the photos to them.
Thanks David!
What thunder should I use on pre slope on cement before I put in my mud
Sorry thinset should I use under my preslope thanks
Hi Daniel,
Whatever thinset you are using for your tile is just fine. It simply bonds the deck mud to the slab, it doesn’t need any special attributes, so any will work fine.
Help! Mine is not a shower maybe next projet. I have a basement electrical room I am tiling but the slope drops off about 2.5 inches. Can I use this same approach the room is about 6×5 feet. Do I need a Precoat for the concrete floor to bond the drypack.
Hi Clem,
Yes, you can use the same method. Just put thinset on the concrete before packing the mud down in order to bond it to the substrate.
Roger, your book is great. On that thinset point, how long should I wait for the thinset to dry before wet mud is applied?
Hi Rick,
You apply the mud into wet thinset to achieve the bond to the substrate.
I put in a shower pre-slope prior to reading this information. I used the Quickcrete Sand Topping mix with water, but I didn’t add sand. The only issue I have noticed is that the mixture shrank slightly around the drain. What purpose does the extra sand provide to the sand topping mix? Would you recommend I redo the pre-slope to include the 30lbs of sand? This is my first attempt at building a shower pan and I want to get it right, so I appreciate the feedback.
Hi Bob,
The extra sand is to prevent it from shrinking (among other smaller things) like it did. However, it’s not absolutely required for a preslope. You can skim-coat over the preslope to fill in that cracking, then continue as normal. It’ll be just fine.
I did a pre-slope using the pre-pitch sticks from MarkE products and all went well. I installed liner with no problems either. When I started looking at installing the final mud deck, I noticed that the drain threads weren’t long enough to put a 1 1/2″ mud deck in. The drain threads are only about 2″ long and if I put a 1 1/2″ mud deck in, plus tile height, plus thin set, this will not leave me any threads to attach drain? I pondered this problem for awhile then decided to just build my mud deck just a tad over 1″ thick at the drain. It came out pretty good and has the proper slope but I’m just not sure it’s okay. I keep debating whether I should tear it all out and get some type of drain extension and go back with a 1 1/2″-2″ mud deck. Your thoughts? Why do manufacturers give you such a short drain when it really needs to have threads that are about an inch or two longer?
Hi Alan,
They do that because it’s enough for a normal shower. The 1 1/2″ thickness of the deck at the drain is the total thickness of the preslope and top slope combined. The pre-pitch sticks are 3/4″ thick at the drain (if I remember correctly) so the top deck only needs to be 3/4″ thick at the drain as well, for a total thickness of 1 1/2″ at the drain.
So I mixed two bags of sand topping with 60 lbs of Quickcrete sand and ended up adding a total of about 6 QTS water incrementally. Something of a pain to mix, so I bet I would have been better off doing one bag at a time. However, I ended up with just a bit extra. Sure seemed like too little water after mixing other concrete products, but it made a ball and I couldn’t squeeze any water out so….
Working it seemed more like building a sand castle than working concrete. About how long can you continue to work this stuff? This was a repair on a 60 year old mortar bed and I did follow your directions about using thin set under the new mud. Is this the same mix the old guys used with the tar paper and wire? I’ll be very happy if this comes out as strong and stable as the old floor.
Hi Chuck,
Yes, it is the same mix. It will continue to harden over time. It won’t be as hard as the old stuff at first, but it will be eventually. 35-45 minutes is about average working time.
Can I use deck mud to level most of my basement floor and feather this to the high point on the floor with a medium bed LFT mortar? This would go on top of a strata mat I already have on top of the concrete slab and bonded with medium bed mortar.
Hi Scott,
It should have been leveled beneath the strata-mat. If it is under 1/4″ difference or so you can make that up with lft. If it is over you would be better off using a self-leveling cement (slc). Deck mud needs to be about 3/4″ minimum.
Roger, thank you for the response. I made the floor relatively flat by using some bags of self-leveling and grinding a large hump out. This is my first time doing this type of work and its my own house so I though I was ok with it not being perfectly level because I had read its mostly important to be flat. I laid out my tile and it looks like there might be a bit of lippage in some areas. Now I have learned about the mud bed and seen pictures of how perfect they turnout, I wish I would have gone that route from the start. However, I am at this point and I was planning to do a mud bed at about that minimum thickness or maybe just a bit more, which would put me just above the highest point on the floor. Then make up that difference with lft in that area. I don’t think I can go like 1 1/2 or 2 inches with the mud bed because of the stair and surrounding rooms. Is this possible?
It is possible as long as all of the mudbed is a minimum of 3/4″ thick.
Over worked myself/exhausted, i bought Quickcrete mortar mix instead of Quickcrete sand topping. Can i use the mortar mix to make deck mud?
Hi Lance,
Yes, but I don’t know what the ratio is in that so you’d have to do it by feel.
“The easiest and most convenient way to get your mixture correct is to buy the quikrete “sand and topping” mix which is sold at all the big home centers. This is already mixed at a 3 : 1 ratio. For a 60lb. bag you need only add 30lbs. of sand to it. ”
Great tips! I found the Quickrete “sand and topping” mix but could you verify what sand I need to get. I was at the big box store and they didn’t seem to have a specific mortar sand available.
Hi Steven,
Masonry sand is best, but any sand sold next to the concrete will work just fine.
Two people curious to know; I’ll be in same situation from project delays and would just as soon repurchase if it’s even remotely an issue. Not many things worse than having to redo new work. Thanks.
Hi Ron,
As you did not reply directly to a specific comment, I have absolutely no idea what these two people are curious to know. I’m answering questions now so I’ll likely get to the other person’s comment shortly.
Great book that helps a lot. Two questions remain. I am building six showers for a CrossFit gym on a new concrete slab.
1. Can I build wood walls down to the slab except for the brick curb for entry? Or, do I need brick on all four sides?
2. You state never to use treated wood. Code requires treated wood bottom plates in basement interior walls. Why not use treated plates on the slab?
Thanks.
Rick, what are you waterproofing with?
Laticrete makes a superb product called Hydro Ban. They make a preformed curb that is 5 ft long. They sell for about $80.
Laticrete also sells great drain/flange pieces that are just over $100.
Set your curb and drain.
Mix your mud as described here. Mud your pan. Wait a couple days, then go over the cement board and pan with 2 coats of Hydro Ban.
I like to start with a coat over all screws and a “liberal” coat in corners/transitions. Then 2 coats.
Then tile away.
If you don’t want to use the curb, you can setup a wood form and pour a cement curb. I’d use a bonding primer on the slab first.
Hi Rick,
1. Yes, provided you use pt wood directly against concrete. You may also require ‘floating’ plates in the wall, with pt wood.
2. I state never to use treated wood for the curb, it would be surrounded on three sides and concrete on the fourth – absolutely nowhere for expansion to go except into the tile. Walls are different, there is only one side with tile against it, it can expand in at least two other directions. I would use treated plates on the slab for the walls.
Roger, my first try at preslopes on the showers went perfectly thanks to your book. Your checklist really helps.
I floated a shower pan the other day with bagged deck mud which didn’t seem to pack as well as usual. Next day I found that my scrap pile (left over mud) didn’t harden at all (crumbly). Then I realized the bags were much older than I thought, 1 1/2 years, stored in garage, but no clumps in them. Pan seems intact, tho more easily scratched than usual. Should I tear it out & reload with fresher mud, or stop worrying?
To clarify, the scrap pile I always pack into a big ball wrapped in kraft paper, and it always hardens. Bed is 1 1/2″ over liner over sloped plywood
Also, I did not use reinforcing mesh, but I packed it VERY well, the scrap ball not so much. Had myself convinced that I should replace until I read some comments about deck mud strength not being a big concern. Getting 2×2 porcelain tile, I always use Versabond or better and prism grout
Hi Douglas,
I’m assuming you didn’t change it? Don’t worry, it’s fine. Although in the future check the dates more closely before beginning.
Hey Roger. My pan is a little smoother than you described. I might have gotten to much cement in the mix. Will it me ok?
Hi Dan,
Yes, it will be fine.
I finished the deck mud final coat above the liner last night. I raised the drain after troweling to get to the height of the tile, or just below tile height. Do we need to caulk beneath the drain and tile in the small gap where the tile grout may not reach the drain threads? Thanks.
If I’m understanding correctly there is a small gap between the drain flange and the deck mud? If so then you need to fill that in with either more deck mud or thinset to solidify it. If that’s not correct let me know what you have going on there.
Yes, that is exactly my question. Thanks for the suggestion.
Is there a better way to get the tile to the same height as the slab for ADA compliant shower floor? I ramped the first prestige of wet mud to the height of the slab. Next, I plan to cut a straight line in the slab where the tile will at the end of the ramp after the final wet mud is applied. I will then use my angle grinder with a 7” diamond blade concrete to match the slope of the ramp down to the bottom of the straight line cut. Thanks for confirming this will work or a better idea. I can send a picture.
A better way than what? I’m unsure what you have going on there, but it sounds (from your first question) that you have a regular clamping drain, and now you’re doing a curbless shower? I’m confused.
The basic answer is that you want your finished shower floor (before tile) height to be flush with the slab outside the shower – then all the tile is installed to the same height substrate. Beyond that I’m having trouble understanding what you have going on.
Thanks, Roger. We have a curbless shower. 2 piece drain installed at slab level. Preslope poured in wet area and then 18” of ramp to zero height above the slab. Will install liner in wet area and add final wet mud in wet area and on ramp without the liner. I thought the top of the tile on the ramp should be the same height as the existing slab. So, this requires me to grind the end of the ramp the height of the tile and thinset. We are staining the slab and no tile on the slab. I hope this better explains. I could send a picture of the presloped floor and ramp.
Oh, I did not know you weren’t tiling the rest of the bathroom. You CAN grind it, but it’ll look like shit in my opinion. It would be a better option to use a transition around the perimeter of the tile where it meets the stained concrete. With ADA specs you can have up to a 3/8″ (I think) ‘step’ transition from one finish to another.
Roger! Just mixed up the deck mud and made a shower floor – never would have gotten up the nerve to try it without your instructions. THANK YOU! Here are some observations from someone who wiggles levers and pushes buttons for a living and has never worked with any of this stuff:
a) Get someone to help you. Having a dedicated mixing guy and a dedicated making the floor guy would have been easier in a cramped little bathroom.
b) It is a process. When you put the first scoops of mud in the shower, you think, this isn’t so bad, kinda hard to mix up, but not so bad. Then you’re frantically mixing and throwing the second and third batches of mud in, wondering how in the *&%^ you’re going to make this stuff slope, freaking out some because the first batch is already getting hard, accidentally poking a couple holes in your Kerdi board with your 2×4 because all you can remember is, “Beat it like the last DMV employee you spoke with.” Then just when you’re sure it’s just a disaster, it starts to look sort of like a floor, and then you can smooth it out some, and things sort of come together.
c) Used a mini flashlight shined across the floor to find high spots in the mud… not sure if that’s the best way, but it seemed to work.
d) Have a respirator/filter of some sort for mixing the dry stuff together. I was lucky I had one handy, it turns out it’s really dusty… and probably not healthful to breathe.
Sorry for the long comment, I’m just stoked it’s done. Thank you again.
Dave
Roger. I have my preslope and liner in andeak checked. putting project on hold until next week and while putting things away noticed my Portland cement says Portland plastic cement. Is this the wrong stuff? If wrong can I leave it in?