What are the Industry Standards for Installing Tile and Stone?

QUESTION

I am in the middle of a new home build construction in Arizona. The builder hired a sub who hired a sub to install all of the tile in the bathroom showers and the tile floor throughout the house. We caught them spot bonding the 12 x 24 tiles onto the shower walls in one shower. They said they had to do it because the new walls were not plumb. However, then they admitted to doing it in all three showers for ease of installation. (?) Builder had them demo all showers and redo them. We were concerned about how they installed the floor tile so builder broke out two tiles. These are also 12 x 24 tiles. They swirled the thinset and then "floated or flexed" (their term not mine) more thinset because the new foundation was not level. The tile manufacturer told me (and per industry standards) that all trowel lines must be going in the same direction. Builder does not believe my documentation, so they are awaiting a letter from tile manufacturer before they will do anything about the floor. In addition, builder installed baseboards first and tiler did not leave expansion joint, but filled the gap in between tile and baseboard with grout which is already cracking. They are also tiles along the baseboards that have exposed cut edges. It appears they took from the scrap pile to fill these in. We are supposed to close on this house on 12/21/2020. I do not know where to turn to. I was under the impression that all registered contractors need to follow the TCNA guidelines for tile installation however, they are clearly not doing this. Any help/advice you can provide would be appreciated. Thank you!

ANSWER

ANSWER - Too often tile and stone installers don't follow industry standards because they have never been formally trained and don't know what are the standards.  They generally have learn from others and assume those methods are acceptable.

Spot-Bonding is not acceptable for tile installations unless it is a wall application and they are using an epoxy adhesive.  For floors in residential dry areas the thin-set mortar adhesive is suppose to achieve 80% continuous contact between the back of the tile and its substrate with all corners and edges of the tile fully supported.   There are recommended methods of applying the adhesive with a notched trowel so the ridges and valleys run parallel to each other that when the tile is placed and beat into the adhesive and shifted perpendicular you get maximum coverage.  But this method is not mandatory.  The installer can use any method of applying the adhesive as long as he achieves the proper coverage.

The industry standards do state that the installer cannot adjust the substrate with the adhesive if the substrate is not properly flat or plumb.  They must use mortar or patching materials to adjust the substrates first.  The standards state that the installer should inspect the tile and substrate before the installation and if there is anything that will prevent them from properly installing the tile then they need to stop the job, advise the client, and do not proceed until it has been corrected.

All tile and stone installations require movement joints to mitigate normal stresses that include leaving a perimeter gap either open and covered with a base or filled with an ASTM C920 resilient sealant. In addition, interior floors need to have movement joints at least every 20 to 25 feet in each direction as well as at al perimeters and changes of planes.  Exterior applications and interior applications subjected to direct sunlight are to have movement joints every 8 to 12 feet in each direction.  Movement joints are to a bond breaker back-up strip and filled with an appropriate type of an ASTM C920 sealant.

It is ok to use remnant or cut pieces of tile to fill in areas as long as they are cut and placed properly and the edges are stoned smooth.

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