Exterior tile has to drain before water sits in the joints
Methods F101 and F102 are the handbook details for exterior walkways over concrete. The Tile Council says mortar contact between tile and substrate should be better than 95 percent, and the thinset or mortar must be rated for exterior use. Joints should be full, compacted, and preferably sealed with a vapor-permeable sealer.
Decks are different details
F103 covers roof decks and F104 covers balcony decks. Many setting-material makers sell drainage systems that are modified versions of F103 so precipitation leaves the assembly. The handbook has no backer-board system for exterior decks. A backer maker may allow one with its own waterproofing. That permission is product-specific.
Water has few ways in
Most tile is impermeable, so water enters through grout joints or through the substrate. Slope to a drain decides how saturated the system becomes and whether it survives freeze-thaw or high heat. The tile itself must be rated by its maker for exterior use, beyond a single lab test.
Source
Fetched 2026-10-11 from Tile Council exteriors FAQ. The sentences above follow that page. They are not a contractor promise.
Related notes
- Tile notes index
- Steam-room grout passes vapor even when the glaze does not
- Frost resistant does not mean the tile survives standing ice
- Backsplash photos
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