Cracks in New Mud Job [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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07-05-2008, 10:11 AM
I have a question regarding a brand new mud job that my tile installer just completed about 2 weeks ago. The mud job is approximately 1,000 sq ft and will be used as a base for marble tile. The underlying structure has 3"x10" wood beams placed 9" on center and span 10' in length with plywood as the subfloor. On top of the plywood subfloor, Tyvek was placed as a moisture barrier and then metal lathing. Before the mud job was complete, the structure was rock solid and the floor was squeak free. As the mud job continues to dry, I am noticing more and more cracks appearing. A couple of the cracks now seem to be very deep. When I walk on these areas, I can see the mud move up and down slightly now. I can also hear what to me sounds like a crumbling noise when the mud moves. Is this normal in a mud job? I am very concerned about this as I do not want to have loose placed in the mud where the tiles will then begin to crack. Please let me know what you think the problem may be. Thanks.

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Crestone Tile
07-05-2008, 10:17 AM
Hi John,

Welcome and sorry to hear about the trouble.

It may have been too wet when mixed and/or not packed correctly. Do you know what the "mud" was? Sand, Portland cement, lime etc. mixed on site? Was it pre-packaged stuff?

Tool Guy - Kg
07-05-2008, 10:17 AM
Welcome to the forum, John.

Assuming the structure is good, it would be helpful to understand how this 1000 sq/ft is mud job is layed out. Like, it is one big rectangle, or does is snake in and out of all the rooms spanning perhaps 20, 30, 40 feet in one direction? Are there any joints, or is it one continuous mud floor? How thick is the mud? And can you tell us what materials were used in the mud?

My questions may help shed some light on the cracks, but vertical movement (crunchy sounding floor) is another story. How thick is the plywood subfloor? :)

07-05-2008, 10:21 AM
the mud floor shouldnt have movement in it.
and, you should also not be walking on a pre gauged floor.
it is not a wear surface and can deteriorate when walked on.
but I think thats the least of the problems here.

07-05-2008, 10:26 AM
Hi, thanks for the quick responses! Well, the mud from what I understand was mixed on site from a portland cement and sand mixture though I do not know the consistency. The mud job was done on the entire first floor so it spans about 7 rooms with each room being basically rectangular in shape. The mud job was done in two days. During the first day, they completed 4 rooms and the next day the remaining 3. I do see the area from where they left off and started the next day looks like a big crack now. The largest room is about 20'x17' and the smallest is about 11'x11'. Since the floor had to be leveled out, it is thicker in some areas than others. However, I would say that the mud is no thinner than 1.5" in any spot. My first guess was that they used too much water in the mix or that the warm weather perhaps caused it to dry to quickly. I am wondering though what can be done at this point other than ripping out and starting all over again.

07-05-2008, 10:38 AM
We have mudded some big floors, even some where we ddn't leave any joints for expansion. I remember one that we mudded back in 95 that was about 900 ft. We mudded the floor about 2 1/4 - 2 1/2 inches thick and left it untiled for at least 6 months. Sheetrock was laid on the floor to protect it from the other trades. During the 6 or so months, huge limestone columns were installed around the big entryway that were 1800 lbs each. 10 columns best I remember. We had cracks going every which way on that floor. I installed a membrane on the mud and never have had a problem. I went back last year to tile their fountain, if there was problems I would know about it. The difference is that we didn't have any movement in the mud when walking on it like you have.

This is it. I musta been leaning or either the house is crooked. :)