It's Not Nice to Fool with Mother Nature II
December 11, 2008
In the last article I showed you what was happening in the basement of a three-year-old, multi-million dollar healthcare facility. The cheapest fix for the basement area was to replace the vinyl with carpet and turn up the dehumidifiers.
/> I’m now going to show you the first floor, main entrance area. The entire first floor is a suspended concrete pan-poured slab that, within the first two years, the stone tile started to crack, excessively! The G.C. has explained this as settling of the building that is beyond his control. I would beg to differ with that statement! True there is movement but beyond his control is what I question. Knowing that there is going to be movement and doing something about it are two very different scenarios.
If you know there is going to be movement in a concrete slab (and there will be) you plan accordingly, with control joints and expansion joints. In addition, the use of soft joints, crack suppression membrane and/or decoupling membrane beneath the stone tile (you are about to see) should not have been an option but mandatory given the expected movement in the suspended slab.
Generally speaking, cracking in tile is due to one of two possible situations: movement of the subfloor or movement of the tile itself. Either way the tile has movement with or without the subfloor. There are other grout-related problems but we’ll leave those alone for now. I assure you improper grouting is not the problem with what you are about to see!
If the tile is moving in and of itself, the grout lines will generally crack and pop loose. Tile movement could be due to improper support of the tile by the mortar bed, or lack of proper notch trowel to include improper back buttering the tile before setting into the thin-set mortar. This is usually identified with a hollow sound in and around the problem area, using the tried and true screwdriver handle tap test.
If the subfloor is moving, the movement is transmitted through the tile and manifesting itself as surface cracks in the tile and generally not following the grout lines. Without removing the tile in the affected areas, we can only speculate (based on past experience) what the cause is! But it’s fun to speculate! Wall Street has been doing it for years. It makes us play other fun games like “What If” and “Cause and Effect.”
Photos 1a and 2 show a typical thin line crack in a low-traffic area, with Photo 1b showing a close-up of the cavity. The crack is in somewhat of a straight line and passes through several tiles. Could this be a saw cut telegraphing due to improper prep of the saw cut? “You Make the Call.”
Photos 3 and 5 are in high-traffic areas and have more of a multi-fracture appearance. Photo 4 is a close-up of the higher-traffic cracks. Also visible in Photo 3 is the lack of metal on the tile’s edge where it meets the carpet. Without it the carpet will eventually matt down, exposing the tiles edge to the vacuum sweeper, and chipping along the entire edge will take place.
Now comes the good stuff! Photos 6 and 7a are of the most frequented traffic areas. Photos 7b and 7c are the same area as 7a, just different angles. Do you think this is a saw cut joint? From the amount of movement transmitted to the tile, could it be an improperly honored expansion joint? Or was the slab fully cured prior to the installation of the stone?
We may never know unless the tile is replaced. And if it is, I’ll get the low down, with photos so we can all learn a little more. Have a great day and thanks again for reading “You Make the Call.”