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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Hugh Tyner

How do you determine how much to mix based on the shower pan size? The stall I’m working on at my home is roughly 32×32.

Reply

Roger

Hi Hugh,

One 80lb. bag of sand and topping mix and 1/2 50lb. bag of sand will yield 3-4 square feet on average with a 1 1/4″ height at the drain. That yield will get lower as your shower gets bigger – the mix needs to be thicker the further away you get from the drain. With your shower figure 3-4 and you’ll be fine. 3 bags of S&T and 1 1/2 bags of sand.

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kevin miller

when mixing mud i prefer the lazy man method (no i dont mean have the helper do it) large batches i use a sheet of plywood or large pan with a rototiller on small jobs on when im by my self i use a small pan or preferably a plastic wheelbarrow tub with a weed whacker with a rototiller attachment ..quick and mixes thoroughly

Reply

May in

Hi

I mixed mortar type S with with sand at 1 to 4 ratio based on the Home Depot dude for my first sloped shower pan and same mix for the final pan.

Is it going to work OK or should I rip it off and start over with sand/Portland cement 4:1 ratio mix?

Also the pan now is very sandy and scratch easy so I’m wondering if the tile and thinnest will stick to it?

Thanks!

Reply

Roger

Hi May,

Thinset will bond to it, but I really don’t know how it would hold up long-term with the type s. It may be fine, and likely is, but I honestly don’t know. I would likely take it out.

Reply

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