QUESTIONHello - I recently had my the ground floor of my house retiled with large (48X8) Mediterrania porcelain tiles. I am very disappointed in the installation and have found 36 voids. I only counted the ones that are greater than 2 inches in length - some go through the entire length of the tile. I am battling with the installer as to what is an "acceptable" void. They tell me that as long as 80% of the tile is solid, it meets requirements. The problem is that these are large tiles and 80% still leaves almost 10 inches of void - Is this acceptable. Your response and help is greatly appreciated, this was a VERY expensive job, and I just want to know if I have a legitimate issue. Thank you for your time.
ANSWERANSWER - First of all not all hollow sounds are voids. Having hollow sounds is not a deficiency and there are no standards addressing hollow sounds, other to say that hollow sounds don't necessary mean it is a problem.
Hollow sounds can be an indication of a deficiency; particularly if some tiles or parts of tiles sound hollow and other parts do not. It could be an indication that there are voids or loose tile or something else loose within the tile assembly; or hollow sounds can be an indication of the type of material or the substrate configuration that the tile was installed over.
Based on your description, it is possible the hollow sounds are voids. The only way to make sure is to remove a few tiles in various sounding conditions for verification.
ANSI A108.5 standard for installing floor tiles says that the average uniform contact area shall be not less than 80% contact except on exterior or shower applications that should have 95% contact. It says that the 80% or 95% coverage shall be sufficiently distributed to give full support to the tile with particular attention to this support under all corners of the tile.
According to TCNA 2016 Handbook and the MIA, for natural stone the minimum coverage is 95% with no voids exceeding 2 square inches and no voids within 2 inches of the corners. All edges of the stone are to be fully supported.
Where there are excessive voids the tile is susceptible to damage if something heavy is dropped on it or something is moved over it with a heavy concentrated load.
The ANSI A108.5 standard does say "average uniform contact" and "sufficiently distributed to give full support" regarding the thin-set adhesive between the back of the tile and its substrate. On that basis, large voids under the tile is not acceptable.
Spot bonding of tile that only gives partial contact leaving large voids is not an acceptable method for tile installed on floors with thin-set mortars.