Using 2" concrete as mudset for ceramic tile [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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03-21-2015, 08:22 AM
I have a small 1/2 bath job which I'd like to turn around quickly.

Is there any reason I can't use 2" of fast setting concrete instead of the portland and sand mix. We're going over a wood sub floor and can isolate it from the wood with tar paper.

I'd like to be setting tiles in 24 hours.

Any tips would be much appreciated!

I can't see why this would be any different than setting tile directly an a concrete slab.....

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03-21-2015, 09:29 AM
Hi Ed, welcome. You said fast setting concrete but do you mean self leveling cement, which does set fairly fast?

I've tiled over dry pack that was less than 24 hrs old. Is there a reason why you are avoiding dry pack mud?

03-21-2015, 10:35 AM
Welcome, Ed. :)

Keep in mind that setting and curing are two different concepts in the world of concrete. Depending upon how your rapid setting material was made to set quickly, it may have not much effect upon the actual curing of the placed mix.

You'd be a whole lot safer using reinforced deck mud in your application as Davy is suggesting. Virtually no shrinkage cracking in properly hydrated mix and the ability to create a very flat, sufficiently porous surface are major advantages over the use of a concrete mix.

If you elect to use a concrete mix for reasons not clear, I'd recommend you use one of the profiled "uncoupling" membranes over it to aid the moist curing and help protect your tile installation. But, as with all concrete mixes, the very most important thing you can do to prevent shrinkage and cracking is keep the mix water to a minimum.

I trust you've evaluated your subfloor structure with an eye toward the substantial dead load of your two inches of concrete?

My opinion; worth price charged.

03-21-2015, 11:45 AM
My thought was to use the fastest curing ready mix concrete at about 2" thick.

Reason is to get the bath back in service in 2 days.

Most of what I've read says to allow the regular portland/sand mix to cure for 48 hours and I don;t have that much time.

Davy said he had done the dry pack in under 24 hours.... is that considered acceptable in the trade, for good results?

03-21-2015, 12:32 PM
My thought was to use the fastest curing ready mix concrete at about 2" thick.You said fast setting earlier, Ed, which would be different from setting. Not sure where you'll find a fast "curing" Portland cement product.

It's acceptable to tile directly to a mud bed immediately after placing it if you want, but I'd not recommend that unless you've got experience with the method. You cannot lift any tiles to check for adequate coverage nor to correct any mistakes. But old guys have set many many acres of ceramic tile that way.

To set over a "cured" mortar bed you still want the minimum of 20 hours cure time before setting the tiles. Then you need an appropriate cure time for the thinset mortar before grouting, which is 24 hours when using cementitious grouts, then another 24 hours or so before light foot traffic, etc.

I think you're gonna have some difficulty with your planned 48 hour turn-around, but that's entirely up to you.

My opinion; worth price charged.

03-21-2015, 04:05 PM
Yeah, in the past we would mud the floor and then put down floor boards (plywood pieces about 24x24) so we could walk on it. Then tile away as we back out.

If we are going to tile the mud the next day, it's good to have the heat on in the house to help set the mud. The mud may be to wet if the house is too cold, say in the 40's or 50's.

Dry pack will erode easily if you get on it too early. It also helps if you slick it down with a flat steel trowel as you back out with the straight edge. Doing that will give it a hard crust on top that won't erode near as easy when you get on it to tile.

John Bridge
03-21-2015, 04:14 PM
Welcome aboard, Ed. :)

I would say no -- for reasons stated by others. Why not use our deflecto (above task bar) to ensure the subfloor is adequate for tile and then use a cement board or tiling membrane?

03-23-2015, 09:26 PM
Great forum, and lots of great advice!

To be safe I'll go ahead with the 4/1 or North American's Shower Base mix which says it's good for up to 3" thicknesses - unless anyone sees a problem with the Shower Base Mix.

As before, I've pretty much got to lay the base and set the tiles in one day, if possible. The reason is that this house is for sale in the realtor's mls, and the agent insists that we can't have buyers even looking at a broken up floor! Grouting and walking traffic can wait.

As cx and Davy mentioned the possibility, I'll plan to tile immediately. I'll place the mud and use the plywood walk pads. or place the mud and tile as I go. I.E. place the 4/1 mix or the shower base mix about 6 sf at a time and then directly apply the floor set mortar with a 1/4x1/4x1/4 trowel notched trowel - then tile. If this is a reasonable approach, the benefit would seem to be that you don't have to walk on the fresh mud, and you have a near finished look right away. This bath is only 3' wide so the screed work will be easy.

I know that cx mentioned that you can't lift the placed tiles to check for coverage and I don't see that as a problem.. while not a pro, I've done ceramic tile work for about 10 years, on and off.

Your comments will be appreciated.

03-24-2015, 05:59 AM
The mud you describe sounds like deck mud.

I think you would be better off mudding the whole floor and then using floor boards to get on it. As you're mudding, pack the mud well as you are spreading it out. If you don't, it may compress under your floor boards when you walk on it.

03-24-2015, 06:29 AM
The mud I hope to use is NA1200, and is otherwise described as a cement based trowelable underlayment good for up to 3" thick over various substrates, if that sounds ok. Other than mixing my own, it's all that the mega tile store Floor Decor has!

Davy, I might not have been in describing my plan, as I won't have to walk on this mud after setting it, if I tile it at the same time.

The room is only 3' wide so I'll pour screed and finish about 3'x2' at a time at a 2" depth - then laying the tile before I pour anymore. That way I'll be working off of the wood subfloor, and won't compress any mud.

Sound reasonable?

03-24-2015, 07:27 PM
Do it the way you feel comfortable with. I've installed both ways many times and like having the floor mudded so I can pop a few lines or lay a straight edge down to set the tiles against. What size tiles are you using?

03-24-2015, 09:21 PM

I did the job today and it went perfectly thanks to all the great advice!

03-25-2015, 12:36 PM
Glad it worked out. :)