What are the Standards for Thin-set Adhesive Coverage/Contact for Ceramic Tile?

QUESTION

I have tiles that were installed concrete slab and have hollow sounds when tap on the corners, edges, and i have voids that are more then 2 in. sq. The sound is coming from the top of the tile since thin-set was not applied correctly by the contractor. I have 12x24. on some tiles i have half of the tile hollow the other half is not. I don't find any tile information stating what the industry standard is. I did go to state license board and they told me that tiles do not need to have thin-set on corners and that voids larger then 2 in. sq. is acceptable. They stated as long as the tile has a little thin-set anchoring the tile this meets industry standard. I came across your blog and your stating different. Can you help me?

ANSWER

ANSWER - First of all, per industry standards hollow sounding tiles are not considered a defect per-se.  Although a hollow sounding tile, or a portion of a tile sounding hollow, can possibly be a symptom of a defect.

There are many reasons why a tile can sound hollow and it not be a defect.  The tile could be installed over a membrane of one type or another.  The underlying substrate could be hollow sounding.  Some reasons why a hollow sounding tile can be an indication of a defect is if there are excessive voids under the tile or if the tile is actually loose.

So it is important to have other evidence of a problem in addition to the hollow sounds to substantiate that there is a defect.  So you can't assume that because a tile sounds hollow that there is a problem.  Although if a portion of a tile floor, or a portion of a tile, is hollow and the other portions are not hollow that might indicate there are voids under the tile, but not always.

So you have remove tiles under various conditions to determine what is causing the hollow sound and to determine if there is any evidence of a defect.

The person at the state contractor's licensing board who told you that it was not necessary to have the thin-set adhesive at corners and said as long as the tile had a little thin-set adhesive contact it would meet industry standards is absolutely wrong.

The ANSI A108.5 and A108.19 standards for ceramic tile or porcelain tile, which is a type of ceramic tile, are the standards that state what are the required thin-set coverage/contact (meaning full contact between the back of the tile and its substrate) is as follows:

  • Per ANSI A108.5 the average uniform contact area, for ceramic tiles installed on floors, shall be not less than 80% except on exterior or shower installations where contact area shall be 95%.  The 80% or 95% coverage shall be sufficiently distributed to give full support to the tile with particular attention to provide support under all corners of the tile.

  • Per ANSI A108.19 for gauged porcelain tiles or gauged porcelain tile panels/slabs installed on floors, in any single square foot under the embedded tile, thin-set coverage will be a minimum of 85%.  Coverage shall be sufficiently distributed to give support of the tile, especially at corners and edges. The required thin-set mortar coverage must be sufficient to provide support under the tiles with no voids exceeding 2 inches square (size of golf ball).  Partially collapsed trowel ridges where the dimension of length or width are less than o.25 in. is not considered a void, nor will it affect the longevity or define an installation as unsuccessful.


 

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