Tiled decks on wood substrates almost always fail due to poor construction practices. Rocket science it is not, but shortcuts most always taken. Hint, if you see the guardrails drilled down into the substrate from above, water damage is occurring. As you can see from these pics, the screw holes are allowing water down into the wood structure underneath. The stucco banding has horizontal cracking underneath all these areas from the corrosion. The last picture shows how guardrails are to be properly installed, that being secured into the substrate, then waterproofed overtop, then tiled and grouted using an epoxy grout, not sanded. This deck was removed last week revealing a $75k complete redo. Caught one 3 weeks ago in North Tampa costing $50k. Anytime you see tile on a deck, your alarms should be sounding. These are not cheap repairs once compromised and even minor signs of damage often point to much larger issues underneath.