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.

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  • Chuck

    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.

    • Roger

      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.

  • Scott

    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.

    • Roger

      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.

      • Scott

        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?

        • Roger

          It is possible as long as all of the mudbed is a minimum of 3/4″ thick.

  • lance shattuck

    Over worked myself/exhausted, i bought Quickcrete mortar mix instead of Quickcrete sand topping. Can i use the mortar mix to make deck mud?

    • Roger

      Hi Lance,

      Yes, but I don’t know what the ratio is in that so you’d have to do it by feel.

  • Steven

    “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.

    • Roger

      Hi Steven,

      Masonry sand is best, but any sand sold next to the concrete will work just fine.

  • Ron

    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.

    • Roger

      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. :)

  • Rick Morrow

    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.

    • Matt Cupan

      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.

      • Matt Cupan

        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.

    • Roger

      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. :)

  • Douglas Adams

    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?

    • Douglas Adams

      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

    • Douglas Adams

      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

      • Roger

        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. :D

  • Dave

    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

  • John

    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?