Neuse Tile Service

Tile installation and service tips from professional installers


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Why can’t you match my stone?

Marble striations

StoneWorld magazine photo.

We’ve been asked to address a problem with a small crack running through the marble in an entrance area. While the underlying problem is movement in the concrete slab under the tile (installed by others), an additional issue is matching the stone.

Natural stones like marble are just that — natural. The chances of duplicating the colors and veining in marble after several years are like finding the proverbial needle in a haystack. As you can see in this photo, marble is cut in quarries (this one 490+ feet deep so far) which produce tons of material each year. This material is shipped over the world, and tracing it back to a particular point of origin is often an impossibility.

While we can order samples, and try to get close, it’s doubtful that we’ll be able to keep the consistent look of the original installation. So, does the customer learn to live with the crack, accept an area of marble that isn’t the same color as the original, or remove the entire area and replace it with a new material?

Here’s the caution from us: When natural stone is used in an installation, it is imperative that extra material be ordered and stored as ‘attic stock.’ Make sure you ask your installer to order extra materials, and be sure you store them in a safe place so they’ll be available should you ever need them to preserve your installation.


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Why is my tile cracking?

     Properly installed tile doesn’t do much moving on its own, so when a tiled surface is cracking, there’s often an underlying problem. A recent article by Katelyn Simpson of the Tile Council of North America gives us some insight:
     In an installation over a concrete subfloor, reflective cracks can result from movement or cracking of the concrete. Concrete continues to shrink long after it’s first poured, and “it causes many shear and compressive forces on the thin-set, tile, and grout. If the shear force exceeds the strength of the bond, the tile may de-bond from the floor. This is also called tenting.”
To help prevent the problem?
       Allow concrete to cure so that any cracks that form can be filled and any distortion of the slab can be ground down. A cure time of 14 to 28 days may be sufficient depending on the thin-set adhesive to be used. Crack isolation or anti-fracture membranes can also be of help. These membranes bond to the concrete subfloor, and then the tile is installed with thin-set over top of the membrane. This can reduce any concrete movement from being transferred to the tile.
     The addition of movement joints can also diminish the stress that occurs between the concrete substrate and the tile. Of course, all floor tile installations should make allowances for movement.
     In an installation over wood, a possible cause for cracked tile is excessive deflection (lack of rigidity or excessive ‘bounce’). Typically, the grout will crack first, and in severe cases, the tile can crack as the compressive and tensile forces bear on the installation.
To help prevent the problem?
     Appropriate joist spacing can minimize deflection. This information from the TCNA information page sheds more light:
            “Traditionally, the accepted minimum requirement for floor rigidity is L/360 – before the tile underlayment is installed. The L/360 standard means that the floor should not deflect more than the “span” divided by 360. If the span of the joists is 10 feet (between supports), then the deflection should not be more than 1/3″ between the center and the end. Frequently, there is misunderstanding regarding deflection between joists. For example, while joist manufacturers regularly meet the standard L/360 criteria for code construction with 24″ on center systems, these floors often have deflection between the joists exceeding L/360.
      Recent research has shown tile to fail under some conditions, when the floor is more rigid than L/360 – in fact failures at L/600 have been observed. It is for this reason that recommendations for floor rigidity are not based on deflection measurements but on empirically established methods found to work over normal code construction.”
Neuse Tile‘s staff can provide consulting and repair services if you have a problem with cracked tile.