Thread: Lots of hollow tiles

The first floor of a slab on grade house had a high percentage of tiles that sounded hollow. What are the main causes of this. There is in floor radiant heat that is delivering water from the boiler to the slab at about 160 degrees when leaving the boiler. Is that a possible cause or a coincidence?

Other causes that came to mind are poor surface prep prior to laying the tile, thin set that was too dry, other ideas are welcome.

Originally Posted by Jim Robinson

... a coincidence?

Other causes that came to mind are poor surface prep prior to laying the tile, thin set that was too dry, other ideas are welcome.

Most likely causes are: a) poor floor prep; b) improper setting of tile (thin set spread out over too large an area and skinned over before tile setter laid the tile on it); c) either a) or b) could cause an even greater problem with heating/cooling of slab producing expansion/contraction stresses on an already weak or nonexistent tile/slab bond.

Originally Posted by Jim Robinson

other ideas are welcome.

Water damage.
*even a small water event of 1/4 to 1/2 coverage left over night.

With the radiant heat in floor you have the potential of a sudden rise in temp across three different materials. The expansion rate will vary between the slab, mortar (if that is the material) and tile. There is a difference in formulation of thin set. Some are more flexible than others. Many installers use a quick setting thin set which is less flexible. But allows them to grout the same day.

If a mastic was used then there could be the issue.

In general:
Trowel without the correct debt of notch.
Thin set was to dry.
Floor to hot or to cold.
Floor not cured enough. (wet)
Sealant used on slab to reduce drying rate for curing.
Tile not pressed into thin set to make complete contact of surface.

I just encountered the same issue on a five year-old entryway and found that none of the tiles were back buttered and the grout was never sealed. In addition, all tile work, in and out of the showers, was layed right against the Sheetrock with thin set, no barrier. Small wonder the owners have a lawsuit pending with the builder.

Originally Posted by Randy Rogers

I just encountered the same issue on a five year-old entryway and found that none of the tiles were back buttered and the grout was never sealed. In addition, all tile work, in and out of the showers, was layed right against the Sheetrock with thin set, no barrier. Small wonder the owners have a lawsuit pending with the builder.

There is no requirement to back butter the tile or to seal the grout.

No barrier is required over the Sheetrock TM, however, the problem may have been the type of drywall used and in the location it was used.

Originally Posted by Jerry Peck

There is no requirement to back butter the tile or to seal the grout.

No barrier is required over the Sheetrock TM, however, the problem may have been the type of drywall used and in the location it was used.

Of course not. Anyone can just meet requirements, if there are any, I see it all the time while I go behind them and do it right. It buys my avgas!

Originally Posted by Randy Rogers

Small wonder the owners have a lawsuit pending with the builder.

Originally Posted by Jerry Peck

There is no requirement to back butter the tile or to seal the grout.

No barrier is required over the Sheetrock TM, however, the problem may have been the type of drywall used and in the location it was used.

Originally Posted by Randy Rogers

Of course not.
.
.
Anyone can just meet requirements, if there are any, ...

Randy,

Then why did you say that it was no wonder they were being sued?

Originally Posted by Jerry Peck

Randy,

Then why did you say that it was no wonder they were being sued?

Because of all the other things that were not done according to "requirements" that turned a $200,000 job into one that ended up over $530,000.

Originally Posted by Randy Rogers

Because of all the other things that were not done according to "requirements" that turned a $200,000 job into one that ended up over $530,000.

Got it.

Your implication was that it was the tile not meeting non-required methods.

Originally Posted by Jerry Peck

Got it.

Your implication was that it was the tile not meeting non-required methods.

Did not mean to but I see I did while addressing the tile issue.

With loose and hollow tile, the way to find out the cause is to lift some of the loose tile.

If the thin set is stuck to the tile, one will likely find dust on the underside of the thin set or paint over spray on the floor (or some other reason the thin set did not adhere to the floor).

If the thin set is stuck to the floor but not the back of the tile, there was something done wrong setting the tile, probably letting the thin set skin over before laying the tile - this is usually caused by one person spreading out more thin set than person laying the tile can keep up with.

Sometimes one may find that the thin set did not adhere to the floor or tile.

Sometimes the thin set is crumbly.

As a side note,
If the "Tile" used was really Marble or Granite, then there is a different set of issues on the correct installation.