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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Don

I’m redoing the shower in my parents basement and have some questions that have come up while reading up on this. There was a rough shower there while I was growing up. There was no tile, just a concrete floor a little higher than the basement floor, a drain, a curb about an inch above that, an overhead fixture and a shower curtain. It was on the unfinished side of a half finished basement. It was rarely used, even in a household with 5 kids and only one other bathroom, so it worked. After I moved out that finished side of the basement was used as an apartment by a series of my siblings and other relatives. Sometime during that time that bathroom was remodeled and finished. A fiberglass shower and enclosure were installed.

Fast forward 20-25 years and my sister moves back into the basement apartment because my parents can no longer care for themselves properly. She complained the shower smelled moldy, The fiberglass pan had give to it and was cracked. Never one to shrink from a big job or tolerate anything that doesn’t smell like bleach she ripped that shower right out of there. Now I get to help put it all back together.

Ripping out the shower pan revealed the crappy job the contractors did putting in the shower. They busted up the original shower floor and curb then tied into the old plumbing with a 2 in. PVC pipe. Then they poured new concrete. The new concrete wasn’t level. It slopes slightly but unevenly toward the drain. That explains the give in the shower floor. They didn’t use shims to support the shower base, it flexed and eventually cracked. They also must have placed the shower pan before the concrete set. There is an impression of the underside of the shower pan in the concrete with the pattern of the fiberglass support ridges pressed into the concrete making concentric square “gutters” across the direction water would flow towards the drain. Any water that leaked from the pan wouldn’t reach the drain anyway. There is a rough bowl shaped depression in the concrete around the stub of the drain pipe about 2 in. deep and 6 in. across. The 2 in. PVC pipe is cut off about the level of the new concrete, so water would just collect in the bowl around the drain stub. It’seems hard to describe, I wish I could attach a photo.

We haven’t been able to find a new fiberglass pan or enclosure of the shower’s size at a reasonable price so I would like to just pour a shower floor and tile the whole thing. I don’t want to add to much height to the base and loose too much head space. For my preslope mud, can I fill that bowl shaped depressing around the drain, then pour it fairly thin, building up the slope around the outer edges and feathering it down to almost nothing at the edge of that depression? How thin can I pour it? Do I have to do anything to make sure it bonds to the existing concrete underneath other than clean it?

Lastly, is it alright to attach my drain assembly to that pipe stub as low as possible before I make the presence bed and mud up to the bottom edge of that drain in the bowl? I could then make an even taper to the outer wall but the mix would be thin outside the outer edges of the bowl shaped depression.

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Ron

You mention that the mix should be 5 parts sand to 1 part cement. Some of the other things you say suggest this is figured by weight. Is the ratio mentioned figured by weight or volume. They are likely different. It turns out in our area sand mix is only available in 80 pound bags not the 60 you suggest even though Quiikrete lists it on their web page. I just want to be sure I am getting a good mixture.

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Rich

I did a stupid thing. I installed the pan before the bottom row of Durock was installed. Do I just need to build up pan another 1/2″-3/4″ after I install the Durock or best to remove floor?

Thanks much

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Brian

Rich, im assuming you mean that you built your shower pan and dont have your durock embedded into it? That is actually the best way to do it. Although durock is really moisture resistant, you really dont want to make more work for it. You should have a gap between the top of your mud bed and durock. I usually leave around a 1/2 inch or so, that way any moisture from the pan wont weap up into the durock. Otherwise you could end up with the durock just soaking in water. Although it may not harm the durock itself, i worry that it could eventually have an adverse effect on your thin set holding the tile on.

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Bill

Hello, im doing a tile shower my floor is a concrete slab i have already installed liner and made my curb i have just put my mud down and it doesnt look right its alot flakey or powdery and when stepping on it it makes little crackling sounds when we mixed it there was a little extra water ..we tried out best to take it out …i used a unknown brand deck mud i tried looking for the quickrete mud but no stores near by carried it please help what should i do

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Justin

Roger,
I mixed the deck mud as directed and needed to pack it in as 3 separate batches due to the size of my shower. There is a crack at the boundary between each batch. I am using Kerdi on top of the deck mud. Are the cracks a problem or will the thinset fill in and be OK or do I have to start over? Would putting down mesh tape like for CBR help?
Thanks for your time.

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Scott Golden

My preslope I did not use thinset over concrete first. I can tell it did bond to concrete. I used quick pitch kit. Should I redo? Getting ready to add pan liner and final mud base.
Thanks for any help.
Scott

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Karl

Hello Roger,
First, thanks for this website. It is a wealth of information that I trust and it gives me the confidence to proceed with my project.

I have a sunken shower on a cement slab that I will soon be rebuilding as it is totally falling apart. For the pan I plan to make a mud base and use the Kerdi system. Also this shower has a horrific step in, the curb is 3.5 inches high and the step down, including curb is 7 inches. I have two questions.

1) I have no idea what is under the current (squishy) mud job, whether it sits on concrete or dirt. After I shovel out the old pan, should the new mud base sit on concrete (i.e. pour concrete up to the desired height) or would having the mud base sit on a bed of freshly packed sand be good enough?

2) I would like to just bust out the curb and just have a walk-in and a step down. Is this feasible? I would like to use a frameless enclosure. How would I keep water from running down the glass door and onto the bathroom floor without the angled curb top? Or should I have a lower curb, or perhaps build up the shower floor so it is no longer a step in?

Thanks again for taking time to help. If you are ever in Jacksonville FL try Bold City Brewery’s Duke’s Cold Nose Brown Ale. Delicious!
Karl

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Dennis

Thanks for the straightforward info. What about coverage? The Quikrete Sand/Topping 60lb. bag indicates about .5 cu ft. of volume. When the 1/2 bag of sand is added, what is that volume? Does it go up to nearly .75 cu. ft or is it less? Can you give an example of how much you use on say a 30″ x 60″ pan (total: preslope and main pan). Thanks!

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Roger

Hi Dennis,

For one bag of s&t and 1/2 bag of sand you’ll normally get about 3-4 square feet of your shower pan.

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Dennis

Your help is great. We have finished the pre-slope using tar paper, wire mesh and 5:1 dryish sand mix. We’ve got a great even slope but the concrete dried with an alligator finish on about 90% of it. Small bumps and crests no more than 1/8″ high. The other 10% dried with the sandy surface just as you describe it should be. We want to avoid this for the top bed so applying thinset is not made more difficult. Any ideas what caused this and should we be alarmed? Thank you for the amazing help.

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Dennis

I don’t think it was the mix. We used the exact formula from the elf and didn’t get it too wet. I wonder if it has to do with not packing it hard enough and having air come up from the spaces in the wire mesh. My helper did keep the surface misted every 4 hours or so for a couple days as she has done with other concrete projects. Would this cause it? Thanks.

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Sarah Baba-Aissa

Hi , I am doing my shower in the basement. we have a 3 inch cement slab, we will add waterproof membrane. After that they recommended us to put mortar mix but Quikrete recommended to put sand /topping mix product on the membrane to create the weight instead of mortar mix. they suggest us toput half Water, half Acrylic

is that ok? we want to put 2 inch layer after that our Tile

Thanks

Reply

Rob

You will need to create a pre pitch with a dry pack mortar before you lay the water proof membrane. First layer is a dry pack creating the pre pitch. Next layer is the waterproof membrane. Third layer is the final layer of dry pack mortar. There are a ton of videos on YouTube demonstrating the proper way to build you’re own shower pan.

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Roger

Hi Sarah,

No, all that is unnecessary. Just use regular deck mud. And you need to create a preslope first, then your liner, then a top slope. Both slopes are nothing but deck mud as described above.

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Ray & BeBe

Like your postings, and your information. clear, simple and not jumbled up will pass it on
Thanks,
“A” Team :whistle:

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Earon

Roger,

I followed your instructions to the “T” and everything turned out great. We just finished applying tile and getting ready to apply grout. our shower looks great. Thanks for this website. It helped me tremendously while rebuilding my shower. Now I am getting ready to build two showers the same way in an investment property we just purchase and will be using your instructions to build the shower pan for them. Again, thanks for the information. :cool:

Reply

James

How thick should the base layer be. To be more specific the layer used to create the slope before the liner.

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Roger

Hi James,

From whatever thickness the bottom of your drain sticks above the substrate up to whatever it ends up at the walls at 1/4″ / foot. So if your drain is 1/4″ from the substrate, your preslope will be 1/4″ at the drain, and if your furthest wall is 4 feet away from the drain, your perimeter will be 1 1/4″ thick.

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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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Roger

Hi Ben,

Yes, but you need to use thinset to bond the new mud to the existing. Or you can leave it, your slope can be over-sloped, that won’t hurt anything at all.

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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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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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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.)

Reply

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

Reply

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.

Reply

Roger

Hi Michael,

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

Reply

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