How to Make Deck Mud

by Roger

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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Scott

Roger,

Thanks for the reply. One more question, is the 4:1 Portland mix generally weak when thin at the drain? Say, where my pre-pitch layer is set? I was careful not yo walk on that later and gently moved a liner over it….when prepping for the final shower pan layer of mud. How would you recommend I fix my spots where the concrete dusted/crumbled upon brushing? Were talking not even a quarter of an inch, or so. Thanks!!

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Roger

Hi Scott,

It is a bit weak on the preslope there before the final slope is done, but it normally doesn’t affect anything negatively. If it’s less than 1/4″ then you should be fine.

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eddieo

No more, liners, no more preslope. One bed, one slope, then kerdi waterproof membrane on top, tile on top of that, done.

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Roger

Hi Eddie,

Yes, I know. :D

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Jess

Having a horrible time doing this .Ive came back after following the instructions as mentioned only to see it was very britaly to the point of any little bit of slight pressure it breaks is that normal ? Did I not add enough water? On a 60lb bag of sand topping quickcrete I added 30 lb of sand and a little more then half a gallon of water , anyways I ebed up talking it out and reworked it I could even bring it back to broken down form with my hands , reworked it added more water not dripping , but wet liked a little better fingures crossed we’ll see what happens

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Roger

Hi Jess,

It’s likely just not packed down wall enough. Remixing it will not work, the cement has already been activated, it likely won’t have enough to resolidify it, but it may.

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Jermey

I am building an shower pan on an concrete floor if i leave the cast iron drain pipe alone and build up from there my deck mud will be about 4″ thick at the drain and about 5-1/2″ thick at the top of the slope. Is this to thick?

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Roger

Hi Jermey,

Nope, it’s fine.

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Scott

Hey there. So here’s my issue. Built up my pre-pan, which admitadely is thin around the drain. The first time pouring the pre-putch layer, a piece ended up popping up near the drain. My second time, things went better off. Is it normal for the mud to be that way? I did mark slightly more then an inch up to get the proper pitch toward the drain. I should also note, I’ve been using the Tile Shop 4:1 Portland cement mixed with only water. Next, after getting the prepitch in, the liner went up and I added to he shower pan level with assistance of the Goof Proof Quick Pitch kit. But due to having to shorten certain sticks on the wall, I mistakingly made each wall go from level at the sides to pitch down to the middle of the wall. Long story short, I added more mud on top, to get the walls level. First off, was that a safe move? I checked that fixed layer and overall 90% is strong and solid…not deteriorating when brushed or with my hand running over it. However, there were four small spots that did dust up and appear as though the mud didn’t adhere. I patched that up again…but should that not work….what are your suggestions? Thank you much!

Reply

Roger

Hi Scott,

The patches should work fine. When using the goof proof shower kit they should be used on the initial (pre) slope, not the top slope. Since they actually slope the floor, and you placed them on top of an already sloped floor, you now have (if done correctly) 1/2″ / foot slope in your shower rather than 1/4″ / foot. The preslope should be sloped and the top slope should actually be a consistent thickness which follows the preslope.

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