Tile
CSI Division 09, Finishes
Ceramic, porcelain, or stone tile installed on floors, walls, or countertops, set into a bed of thin-set mortar or adhesive and finished with grout between the joints, a finish chosen as much for water resistance (bathrooms, kitchens) as for appearance.
Why it matters
Tile installed in a wet area depends on a properly waterproofed substrate underneath it: the tile and grout themselves are not the actual waterproofing layer in most modern assemblies, a common misconception that leads to water damage behind or beneath tile that looks perfectly intact on the surface.
On a real project
Before tiling a shower wall, the installer applies a waterproofing membrane over the substrate first, so the tile and grout serve as the finished surface while the actual water barrier is the membrane underneath, not the tile joints themselves.
Who this matters most to
A specialty tile-setting crew installs tile to precise layout and leveling tolerances, since an uneven tile installation is highly visible in a finished space. A Quality Control Manager confirms waterproofing is properly installed and tested in wet areas before tile covers it, since it's the last chance to catch a waterproofing gap.
Where this goes wrong
A tile installer sets tile directly over a substrate in a shower without confirming a waterproofing membrane was installed underneath first, assuming the tile and grout alone will keep water out. Water gradually works through the grout lines over months of use, and because there's no membrane behind it, the moisture reaches the wall framing, causing hidden rot discovered only once it becomes extensive.
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