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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Ferrell Fuller

Yea, so i didn’t mix the sand in with the Sand and topping mix but instead used the directions for 3 quarts of water to mix it. I poured my pres-lope last night and stumbled on this article. It went in very dry and looks great after looking at it this morning. Am i screwed? Its on a concrete floor and i obviously will be doing the liner on top of that with the rest of the instructions you’ve sent. Thanks in advance!

Reply

Roger

Hi Ferell,

It will be fine for the preslope.

Reply

Roland

Thanks Roger. I did just that. Had to chisel through slab. I ended up cutting the pipe too short so had to put in a coupler to bring it back up to the correct height. But I was already through the slab so just had to dig a bit. I’m going to use the Schluter pan instead of a mud pan. We shall see. Have to level the shower floor first.

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Mark

I got zealous with a nylon scrub brush in two sections (used a pitch kit) of our pan that seemed sandy and crumbly. I was concerned that I mixed the final batch too dry or it had been too long. My thought was to go down to solid and fill/patch. I now have some very large divots and I even went down to the liner near the drain in one spot. I know… :(

Can I patch affected areas with fresh mud? I noted your reference to applying thinset to bond old deck mud to new. Thinset watered down? use a lot/little? Immediately apply deck mud or cure/time?

Thank you for your time and sharing your knowledge. Great forum

Reply

Roger

Hi Mark,

Yes, but you need to use thinset thinned down to the consistency of pancake batter, put it down, then the mud, they’ll cure together.

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Roland

Hello, I am using a Schluter drain and looks like my drain pipe is not low enough in the concrete slab to install their pre-fab shower pan so i will need to install a mud one. When I place the schluter drain in drain pipe there is about 2 3/4 to 3 inches from the existing slab to the bottom of the drain flange. I am not sure if the mud pan can be as thick as 3″.

Please advise.

Thanks Roland

Reply

Roger

Hi Roland,

Yes, it can be 3″ thick at the drain if you need it to be. Although it would be easier to cut the stub pipe down a couple inches, unless it’s cast iron. :D

Reply

Denise

Hi Roger
I am using a dry pack installation for my shower pan. How many days should the new shower pan cure before applying Redguard waterproofing?
Thanks
Denise

Reply

Roger

Hi Denise,

Redgard requires 3 days.

Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.

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Patrick

I am creating a new shower in a converted bedroom space and am at the pan stage. The subfloor slopes slightly away from the drain hole. I have already RedGuarded the subfloor. What is the best material to use to level the subfloor, over the RedGuard, prior to putting in the membrane and deck mud? Also how thick should the leveling material be? Thank you for your time. Pat

Reply

Roger

Hi Patrick,

Why did you redgard the subfloor?

You need to create a preslope – that is done with deck mud. When you do that you’ll have a consistent slope from the wall to the drain. Then your membrane, then your top mud deck. The floor unevenness will be compensated for with deck mud when you do your preslope.

The deck mud needs to slope 1/4″ / foot from the wall to the drain, the thickness will depend on how unlevel your floor is. Your preslope should be a minimum of 3/4″ thick at the drain.

Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.

Reply

Elaine Hughston

Hi
we put down 4 to 1 deck mud preslope but screwed up and didn’t have enough. Waitedd for it to dry and then packed another layer of mud. The guy at Mapei (used their 4:1 floor mud mix) said to use quick patch concrete premix to fill in small dips and then redgard on top.

Question 1. Will the red gard stick to the grittyy deck mud or just create a sandy guck

Question 2. Is there an issue with adding deck mud on top of deck mud or what would help them bond.

thanks

Reply

Roger

Hi Elaine,

1. It will bond just fine. It’s normally much easier, though, to first skim-coat it with thinset, let that cure, then install the redgard.
2. Use thinset over the existing to bond new mud to old.

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Joy

Don’t know if last question made it to you–So– we are creating a shower on a concrete slab (replacing a tub). Ours will be 4′ x5′ . Do we need to have two different sections of mud in order for proper waterproofing? What is the average thickness of the mud at the edges of the pan. In the pics, it only looked like no more than 3 inches total with the felt, wire mesh, membrane, and the two layers of mud. Please help :)

Reply

Roger

Same answer. The total thickness at the perimeter is normally between 2-3 inches.

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Joy

REALLY need your input. My husband and I are tearing out a whirlpool tub and outing in a shower. Looked at purchasing a shower pan ready for walls and tile. Would like to save money by creating our shower over our concrete floors. Which steps, in your system for building the pan, do we need to use for proper waterproofing? Do we need two layers of mud?

Reply

Roger

Hi Joy,

It depends on your waterproofing method. If you are using the traditional method on the floor, then yes, you need both layers.

Reply

L

Hi Roger
While recouping from surgery I will pick your brain few times. But in a discussion with a Yankee construction fellow, he recommended some sort of two part epoxy between my concrete base slab and what will be my deck mud/slope. I still lean to thinned Laticrete as you recommended and that I have a large bag of anyway. Any thoughts on what he has used?
You are my boss….
~L in Naples FL

Reply

Roger

I have no idea what he may be suggesting. Not required and a waste of epoxy in my opinion, the laticrete will work just fine.

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john

I need to build a wheelchair accessible shower. I am going to use a 55″ linear drain the shower will be 60″ deep. I can gain approximately 1 3/8″ by dropping the floor down to joist level. the slope to the drain will be about 1 1/4″ over 60″ if I make the preslope with thinset I really wont have any room to use deck mud. can I waterproof with a redgard type membrane right over the thin set or will this produce a problem. I do not want to cut the floor away if I can help it at all. Thanks for any assistance.

Reply

Roger

Hi John,

You do not make a preslope with thinset. Ever. It is made with deck mud. And yes, you can go right over a single slope of deck mud with a topical membrane.

Reply

Kip

What is the thinnest you want to have the concrete at the drain edge? Is 1/2″ acceptable? I have 2 1/2″ at the out side edges of my shower pan area.
Also this is over a solid wood sub-floor and wood joist sub subsystem.
Thanks for the help

Reply

Roger

Hi Kip,

You don’t want concrete at your drain edge. If you do it will crack. You can have 1/2″ DECK MUD at the drain edge if you need. I’m sure that’s what you meant, right? :D

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Vanessa

I have an uneven concrete floor that used to be a porch now it’s an enclosed room, would the 5:1 deck mud work to level and then lay tile? Is there a brand name? I don’t want to have to replace the $1000 tile I’ve purchased for this project. I am already trying to correct someone else’s work. Any insight is greatly appreciated. Desperate homeowner

Reply

Roger

Hi Vanessa,

Deck mud (5 to 1) would be the ideal solution for you. There is no brand name, it’s sand and cement, it’s all the same stuff.

Reply

Steve

I did a dry pack floor in a room 15′ x 15′ to raise the height anywhere from 2.25″to 3″. When I secreted the floor smooth there were places where a thin top layer would drag away, and I had to smooth it again with a trowel. When the floor was dry some of these spots came free, leaving small 1/8″ to a 1/4″ uneven spot randomly around the floor.
I will be placing 12” x 24” Porcelain tile directly on the cement floor once it is smooth.
My question is what is the best method to top and smooth the surface?
1. Use 3:1 Sand topping mix thin enough to trowel a smooth surface? Will this bond directly to the dry pack?
2. Use a self leveling cement, if so do I need to seal the dry pack first or will SLC bond ok to the dry pack?
3. Just trowel a thin layer of modified thinset to produce a smooth surface and allow to dry before setting tile?

Thank for your help.
Steve

Reply

Roger

Hi Steve,

2 or 3 would work fine. 3 is much easier. Yes, slc will bond fine to dry pack. Do not seal it first if you go that route.

Reply

chris

Hi Roger.
The people at lowes told me to use sand/topping mix for filling in between pavers. Just sweep it in and wet it. But I keep seeing it called other stuff and am wondering If the topping mix will work. :?:

Reply

Roger

Hi Chris,

I don’t see why it wouldn’t work. I’ve never done it, but it should work just fine.

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Joe

Hi Roger,

Your Traditional Shower Manual has been a great help. I am getting ready to put fat mud on the curb. My mud is the pre-mixed Deck Mud in a sack. I’m guessing that I will still need to add lime to make it sticky but wanted to ask you before I cause my dog to burst into flames.

Many Thanks,

Joe

Reply

Roger

Hi Joe,

Yes. You’re dog will be fine. :D

Reply

Hans

just a question when I used to work for big companies and we would do massive floors for schools or shopping centers was the deckmud mix one shovel scoop of cement and 12 to 14 shovels of sand?

Reply

Roger

Hi Hans,

I don’t know, I didn’t work with you. :D Mine have always been one of cement and 4 or 5 of sand. If you used 12 to 14 then you weren’t mixing deck mud, it would probably be just gray sand. :D

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Paul Haynes

Hi Rodger

Love your site. Wondering if you you used a different mud mixture for for covering the the actual curb than is used to make to shower floor. Also, why do you say to never used pressure treated lumber for the curb material.

Thanks

Paul

Reply

Roger

Hi Paul,

The curb is created with fat mud, or wall mud, which is just like deck mud except it has lime in it to make it sticky. Pressure treated lumber, when NOT exposed to moisture (like under a waterproof curb) will slowly dissipate the infused moisture present in the wood and begin to shrink and twist. Not a good thing beneath your tile.

Reply

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.

Reply

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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