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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Kevin Link

You mention the mud should be sand and regular portland cement. I heard that “Sharp” sand was the best, do you have a preference for sand type?

Reply

Roger

Hi Kevin,

Sharp sand is best, but difficult to come by in some areas. I most often use the regular quikrete sand sold right next to the sand and topping mix.

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James_morrell

Hi. I have a space from the deck/base to the bottom of the wall. Do I do the deck mud first and come back after it is dry and fill in the wall space with deck mud

Reply

Roger

Hi James,

You can if you want to.

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John

I only have 1/4 inch between my hardiebacker shower floor and the top of the bottom flange. This means that my preslope will only be 3/4 of an inch at the wall and 1/4 at the flange. Will that work?

Reply

Roger

Hi John,

Yes, that will work fine.

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Jay

Do recommend “Play Sand” or “Multi-Purpose Sand” for the 30lb mixture ratio to the 60lb Sand Mix?

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Roger

Hi Jay,

The multi-purpose.

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CountriSquire

Hi Roger,

Plenty of You-Tube and just finding your site and it looks like the best yet across the baord.

Admittedly, I haven’t read the plethora of info yet, but can you take a quick jump to Chapter 10?

I’m doing tub to floor shower conversion on concrete slab home. I’ve removed concrete and dug well below to make the P-trap location 180 degrees opposite and the finished new shower drain will now be about two feet inward.

I’m thinking the surface of the flange that will be below the ‘membrane’ should be located about 1-1/2″ above existing slab floor when I plumb it.

1) Does that sound correct for ~ 3/4 thickness on pre-slope and the same for the mortar bed above. Or should I allow 2″ to 2-1/4″ to allow for thinset and tile thickness as well? Tile not yet selected.

2) When the plumbing is done and the hole back filled should I fill the entire slab opening thickness with concrete or mortar? Now aprox. 14″x 28″ or so – this includes old area where tub drain came up ~ 2″ out from sill plate.

3) If using bricks instead of 2×4’s for curb, how does one secure the membrane on the top and outside surfaces of the bricks?

Let’s leave it at those three for starters, but maybe more as read the pdf’s.

With all the bucks involved, a re-do is definitely notan option.

With the sincerest of thanks!

Reply

Roger

When you say the ‘surface of the flange which will be below the membrane’ I assume you’re speaking of the lower flange? I also assume you’re using a regular pvc membrane and a double layer shower floor? If so…

1. You want the lower flange to the the depth of your preslope. So 3/4″ high. The membrane gets sandwiched between the upper and lower flanges, then the barrel threads into the upper flange – that is what lowers or heightens your drain for the finished surface.

2. It can be concrete or deck mud, either one works.

3. You wrap the membrane over the curb, then bend wire lath in the shape of the bricks and fit that down over the top of it. The lath holds the membrane in place.

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Tuan Huynh

Hi great site by the way !
I try to build my shower and I going to use schluter foam

I have 2 questions
1st can I cut down a schluter foam ?because I like it’s lower
2nd how do I make it bonds to the concrete ?

Reply

Roger

Hi Tuan,

Yes, you can cut it down but it will be difficult to get it consistent. It is installed with thinset.

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Tom

Now that mine is installed, what is wrong with not having a pre-slope between the liner and top layer? Hopefully not much! Thanks for your time.

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Roger

Hi Tom,

There will be a layer of water that sits below the drain itself. It will NEVER drain, and it will be there permanently. A cesspool for all sorts of nasty things to grow.

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Kamran

Can you elaborate on the preslope? What does it meant and where will the water sit? In our implementation we have plywood, then cement board, then shower liner and then the mud pan that is sloped. Does this work?

Reply

Roger

Hi Kamran,

I already elaborated on it here: Shower floor for tile If your shower liner is flat on the cement board, without a slope beneath it, then no, it doesn’t work. You need a preslope beneath it.

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