Cracked Natural Stone Tiles

[t majchrowski]

We have natural stone 12" by 12" tiles covering our dining room, kitchen, and hall areas. There are fine cracks every three feet throughout the dining, kitchen, and hall areas across the width of the areas. The dining room and kitchen areas are about 24 feet long and 12 feet wide with an island in the kitchen area. The hall is about 30 feet long by 3 feet wide. The substructure is plywood on top of 7/8 in. Trus Joists. The joists run perpendicular to where the cracks occur. The joists are around 39 feet long and around 19 inches apart. The maximun joint deflection is supposed to be L/480 live load and L/240 total load. The stone tiles are placed on backerboard. I have lifted the island and see that the backerboard is 5 foot by 3 foot and is stapled in place. The cracks appear to occur at the backerboard seams.

Our prime contractor and the tile installation contractor say they have never seen anything like this and don't know what the problem is.

Has anyone seen anything like this? Does anyone have suggestions?

Thanks. Tom and Pat

[Mike2]

Hi Tom and Pat. Welcome to the Forum.

Tell you what....bet Prime Contractor has heard this complaint before....laying natural stone tile over flooring systems designed for L/240 live load. Standard practices for stone call for L/720 deflection minimum.

Don't know what else to say. Other's will be chiming in.

[RandyL]

Firstly you natural stone floor needs a rating of L/720 rather then 480 which wuold have been sufficisnt for ceramic or porcelain tile. So you deflection is too high. It may also be caused by your backerboard sheets not being taped when they were layed. Also, the boards need to be aniled or screw inplace with the appropriate fasteners in the appropriate fastener pattern, not stapled. Did they embed the backerboard in mortar before they layed them?

I'm not one to make judgement, but when ever I hear someone say "I've never seen that happen before" is either not being honest, or, they really are being truthful and have never seen it before because they've never done it before.
Hope this helps.

[John Bridge]

Hi Tom and Pat. Welcome aboard.

I'm really sorry to hear this. I concur with Mike and Randy. The insaller folks either have a clue or they don't. Just about every established convention was ignored in your installation.

[cx]

Welcome to the fray, Tom and Pat.

I'll be the first to admit I don't understand some of this description:

The substructure is plywood on top of 7/8 in. Trus Joists. The joists run perpendicular to where the cracks occur. The joists are around 39 feet long and around 19 inches apart. The maximun joint deflection is supposed to be L/480 live load and L/240 total load.

In particular, I don't understand the description of a "7/8 in. Trus Joist". Truss Joist I comprende OK, but not the 7/8 inch. Can you tell us a little more about the joists? In particular, the depth of each joist, and a model number if you can see one stamped on there somewhere (I'm assuming they are Weyerhauser's Silent Floor System).

And we are to understand that the joists are a clear span of 39 feet with no intermediate support? That's a fairly long residential span, is why I ask, and to get L/480 deflection with 19.2 inch spacing a fella'd need pretty deep joists.

As has been pointed out, the standard deflection is far higher than your rating, if indeed you have that much floor. Did you get the specs from the builder or from an engineer or the manufacturer?

We also need to know what's under the backer board. With 19.2 inch spacing, you'll need to have a lot of plywood under there in two layers. Find out what they gave you as a subfloor. Then find out what's directly under the backer board. If it's stapled down, I'm a little suspicious that it may not have thinset under it and that the joints may not have been taped as required. Do you know if both those things were done? And the name of the backer board may be helpful, since it's stapled.

You may have a number of problems ganging up on you here. I'm also gonna agree with my friends Mike and Randy that if your builder/tile mechanic have ever done this installation before, they've seen this problem before. I'd be questioning them very pointedly about this installation.

My opinion; worth price charged.

[Mike2]

Backerboard over 19.2 OC joist spacing....hummm. Must be some speciality stuff I reckon. Surely Prime Contractor would not pewt regular CBU down on that floor. Whadaya think bbcamp?

[tileguytodd]

This sounds more like an I Beam type joist than a truss joist and 39 feet is mucho long if it unsupported.
Stapling CBU?? Unnacceptable.
I would bet there is no bed of thinset below either which is also unnaceptable by every board manufacturer.
Even if the GC or engineer were wrong,the tile installation company should know better than to install over those conditions.
Tile company is 100% at fault here if only for improper substrate installation and thats not counting all the other mistakes.This is a sure win in court with a few photos and a few installation guideline downloads from manufacturers websites.If your deal was with the general contractor you need to go after him and he will have to go after the tile company.If you paid the tile company direct and they were reccomended by your GC name them both.

This is so flagrant a disregard for acceptable practices,punitive damages are a good possibility.Sounds like willful negligence to me .Perhaps our esteemed legal eagle would have a better idea as to that particular possibility
Some companies need to be taken down hard as they give the entire proffession a bad name.
Those of us who work hard to do a proper job have to try to compete with these hacks who are not interested in the craft,just the buck and how fast they can steal it.

[bbcamp]

Everybody's covered the basics, except the contractor. I can't think of anything he did right.