Speculating what is underneath floor tiles in a room

[daluu]

Just noticed something unique in an area of tile. On the surface the tiles look fine, and didn't notice any cracks. But knocking on the tiles in one are produces a different sound. Normally, the sound is sorta like knocking rocks against concrete, but in one area, it sound hollow, with a "tik" kind of sound. Wondering if anyone has ideas on the sound difference.

See the either video for more details (on sound, even if the video quality is crappy).

http://dlshare.s3.amazonaws.com/temp/VID_20120122_132402.avi
http://dlshare.s3.amazonaws.com/temp/VID_20120122_132402.mpg

What might account for the difference in sound? Is the area under that part of tile a pipe, or something?

Probably be hard to verify w/o tearing out tile and flooring underneath or the walls adjacent to it.

 

[PrenticeBoyofDerry]

It's more than likely an area where the adhesive screed under the tile is not bedding between the tile and floor.

 

[Richard C]

Could be a pipe duct but unlikely it would only be under one tile. As already said, most likely cause is insufficient adhesive under the tile or the adhesive bond has failed & all that's holding it in place is the grout.

Floors should be laid on a solid adhesive bed >100% coverage or the tiles can crack under load. Some cowboys also use dot & dab adhesive to fix rather than a troweled solid bed which is even worse.

 

[daluu]

Thanks for the replies. Didn't know about that, good to know. Guess only fix in this case would be to rip out the affected tile(s) and re-tile it back in, but perhaps better to leave alone until it cracks then replace?

Also, would water seepage through the grout also result in adhesive loosening up to cause this? Or adhesive sticks one applied and dried?

 

[Richard C]

Everything is dependant on the tile adhesive but if it’s a quality waterproof adhesive then, no, it shouldn’t be affected by water. It’s worth remembering though that apart from epoxy products, waterproof adhesive & grout is only "waterproof” in the sense it won’t (shouldn’t) disintegrate when wet, it’s not impervious to water. This is why it’s important the tile base is truly waterproof if regular wetting of the tiles is going to occur.