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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Ben

hi,
a quick question, I layed down the second layer of mortar in my shower after installing the pan liner and realized I made the pitch too steep. is it ok to add more mortar to the existing mortar after it is dry?

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Jim

Hi Roger,

I might have an issue. I just did my pre-slope but I think I may not have added enough water. How can I tell if it’s hard enough? It seems overly sandy to me.

Plus, there’s a spot that didn’t get hard and left a ‘dent’ when brushed away. Can I just add more mortar to fill this dent?

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jim

building my own tile shower. Installing a linear drain so I presloped my sub floor and put down thin bed of mortar by the drain to get the best taper to the drain. I’m ready to put my liner down and then complete the top mud deck. At the thinnest point,my mortar will be about1/2 to 3/4 of an inch. Is that enough thickness for the mud deck to remain stable or is there a better mixture or product for thinner applications.

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Chris

Just a heads up that adding 30 lbs of sand to Sakrete sand topping and bedding mix will not work for a shower pan (I guess this product is different than Quikrete sand topping?). Anyhoo, the Sakrete product has instructions for a shower pan…follow them and only add water :bonk:

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Chris

I’ve never used the Quickrete sand topping mix, but I did follow these instructions with Sakrete Sand Topping and Bedding mix and I will say that adding 30lb of sand to that does not work. Follow the manufacturer’s instructions for a shower pan and just add water :bonk:

McD

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Shane

The Sancerre is what I have and I was going to mix in sand to achieve a ratio closer to 5:1. Why are you saying that I shouldn’t do this if the Sankrete topping is premixed at 3:1.. You just confused the hell,out of me?

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Chris

I’ve never used “Sancerre” so I have no idea about that product. I’m saying that I added sand to Sakrete sand topping mix and it crumbled. So I redid it following the manufacturers instructions (no added sand) and it turned out fine. If using Sakrete sand topping mix, don’t take my word for it. Read the shower pan instructions on the package…I should have.

Whatever product you use, you can always pack a pie tin with a very small batch and test it. Might save you some frustration.

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Joe

What is the best way to prevent moisture from wicking up the backerboard from the mortar bed? To not submerge the lower edge of the backerboard in the mortar bed?

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Chris

The mortar should be just moist enough to pack…this isn’t really an issue. Just like the mortar bed, the backerboard will dry out during curing.

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Joe

Today, December 8, 2015, I found Quikrete Deck Mud in 50lb bags at Home Depot. The spec sheet for it says the design mix is 5:1, so that appears to be exactly what you recommend.

It also says to use acrylic fortifier, but I’m not so sure that would be necessary or beneficial in this application (mortar bed shower pan).

Thanks for the great web site and info!

I’m still a bit uncertain as to the surface the pan will rest on. Some sources say to dump the mud right on the floor, some say to spread thinset right on the floor then dump the mud onto it, and others say to cover the floor with tarpaper (felt), galvanized lath stapled down, and then dump the mud on that. The tarpaper will prevent the wood floor from sucking all the moisture out of the deck mud before it can fully cure. It seems to me that adhering the deck mud to the subfloor would not be especially important, considering it has no place to go, hemmed in by the shower walls, and the amount of weight on it (the mortar bed and tile). In other words, I don’t see how the pre-pan can move after curing no matter how badly it might want to. Using tarpaper between the subfloor and deck mud makes plenty of sense to me, but I wonder why more than one source says to start by dumping the mud right on the plywood subfloor, or thinset as an adhesion layer right on the plywood subfloor, and if one uses metal lath stapled to the subfloor through the tarpaper why adhesion to the tarpaper would be an issue at all.

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Chris

You don’t need to adhere the pan to the subfloor or worry about the subfloor sucking the moisture out. If it is adhered it to the floor, you increase the chance of cracking. You do need some breathable fabric underneath the pan, with lath on top of that. I used garden fabric.

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Jacob

I am beginning a walk in shower in my upstairs bathroom. I took out the bathtub and stripped it down to the rafters and laid an inch and a half of plywood down for my subfloor. My worries are that there’s about a quarter inch sag in the rafters, I guess from over time foundation issues. Could this serve any major problems? Before there was a cast iron tub sitting in that spot. Mainly I’m worried about the deck mud cracking thus popping tile

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Chris

The pan will take on the shape of the sag. Should be fine.

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bill

is sakrete sand and topping mix a ratio of three to one , sand to portland also.

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Jay

Can I install the membrane the same day as the preslope? Or does the mud need to cure?

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Roger

Hi Jay,

In a traditionally waterproofed shower you can lay the liner over the preslope right away.

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Bob

It is correct to do two layers correct? One thinner with slope and then lay pan and then another thicker coat?

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Roger

Hi Bob,

Yes.

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Chris

There are products such as Kerdi membrane and Laticrete Hydro Ban where you can lay the pan in one layer and apply the membrane to the top. These require a drain specific to this type of installation.

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Ernest Phillips

I am installing 2 shower floors, one, on wood sub-floor, the other a concrete slab. I am using the Kick-pitch/slope plastic strip kit.
2 questions –
#1 – Have you used that system and any pointers?

#2 – Mud mix – I saw the Quikrite Sand & Topping – how much more sand do you add (30 lbs.?) I’m sure you do not mean weight it, is that like one bag sand & topping, to an additional half bag worth of mason sand? I have an entire truck load of mason sand on site. This mix is so important I want to get it right.( At Lowe’s they sent me to the tile dept. to buy the 4-1 mix at $15.00 per bag, sold by the grout, compared to the Quikrite products in lumber at $5.00 a bag.)

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Roger

Hi Ernest,

1. Not really, it’s fairly self explanatory. It works well.
2. 25 lbs. per 60lb bag of s&t mix. Yes, 1 bag to 1/2 bag.

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Mathieu perreault

Hi, great site by the way ! I have a question about a mortar bed on a concrete slab? Is it the same proces than on a plywood? Do I need a tar paper plus a metal lath? I’ve seen many contractor put some thin set on the concrete and and mortar bed after and membrane! What do you think? Thank you

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Roger

Hi Mathieu,

Over concrete you just put down thinset then the mud over it. The thinset bonds it to the concrete, the same thing that the lath does over wood.

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jeff dougherty

Great info dude, I,ve done a lot of tile but the floor I remember not watching. I am going old timer, as I,m a sheet metal mechanic by trade. I’m fabricating a copper pan then mud and lathe in the pan. That way, I will know the harwood floors won’t be threatened by a bar of soap someday!

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Dave Law

I doing my centre patio. It has a 1″ wooden subfloor. I got a roofer to line it, with the finish being of a gritty texture. This replaced the old metal pan which had rusted out. My next step is to slope quikrete deck mud down to the floor drain, 2″ thick at its thinnest point. Next is redguard, thin set mortar and finally tile. Am I missing any steps?

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Roger

HI Dave,

Not that I can see.

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Nick

Question for you.
I have a shower i am remodeling and will be creating a mud bed from your directions. Right around my Drain, i have a cutout in the concrete slab(I assume from construction of the house) that was backfilled with sand. It extends out from the bottom flange of the drain about 4 inches on each side. when doing my pre pitch mortar bed, what would be the best way to go over that sand? should i first cover the sand in concrete to give a solid ground for the bed to lay on? I dont know how well the deck mud will stick to the sand that has been filled in.

Thanks
Nick

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Roger

Hi Nick,

The deck mud doesn’t need to bond to the sand, you can just pack deck mud into that space, it’ll be fine.

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Kyle

Concrete slab with shower drain bottom flange level with concrete. Can I smear the thinset then deck mud very very thin near the flange then ¼ inch per foot out for my preslope? Or do I need to have a min thickness for the deck mud at the lower flange?

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Roger

Hi Kyle,

You can do it with the thinset and thin bed at the drain for a preslope.

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Michael

i have been on you site for the last 2 days trying to find a way around pulling my pan up and redoing it. long story short I did not preslope under my pvc pan liner. I used Tec thick mud bed directly on top but now I am afraid I will have mold grow in the shower since there is no pre-slope under the liner. Is there an issue that the floor drain flange is flush with the subfloor? it was installed by the plumber prior to me starting on the shower. Thanks in advance.

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Roger

Hi Michael,

No real issue with the drain, but you do need a preslope beneath your liner.

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