A contractor is installing ceramic tile over a concrete slab. The slab has a moisture emission rate of 4.5 pounds per 1,000 square feet per 24 hours. What action should be taken?
Correct Answer
B) Apply a moisture barrier before tile installation
Moisture emission rates above 3 pounds per 1,000 square feet per 24 hours typically require a moisture barrier to prevent tile adhesive failure and potential mold issues.
Why This Is the Correct Answer
CORRECT_ANSWER - When moisture emission rates exceed 3 pounds per 1,000 square feet per 24 hours, a moisture barrier is required before tile installation. The measured rate of 4.5 pounds exceeds this threshold by 1.5 pounds, indicating significant moisture that could cause adhesive failure, tile debonding, and create conditions for mold growth. Installing a moisture barrier will prevent moisture from migrating through the concrete and compromising the tile installation.
Why the Other Options Are Wrong
Option A: Proceed with installation using standard methods
Proceeding with standard installation methods would be inappropriate because the moisture emission rate of 4.5 pounds exceeds the 3-pound threshold. This would likely result in tile adhesive failure, loose tiles, and potential mold issues due to trapped moisture.
Option C: Wait for the slab to cure longer before installation
While waiting for additional curing might reduce moisture levels, there's no guarantee the emission rate will drop below 3 pounds per 1,000 sq ft per 24 hours within a reasonable timeframe. The immediate and proper solution is to install a moisture barrier rather than delay the project indefinitely.
Option D: Use a different flooring material
Changing to a different flooring material is unnecessarily drastic and costly when the issue can be properly addressed with a moisture barrier. Ceramic tile can still be successfully installed over concrete with elevated moisture levels when proper moisture mitigation measures are taken.
Memory Technique
Think '3 and FREE' - 3 pounds or less means you're free to install without barriers, above 3 pounds means you need protection
Reference Hint
Florida Building Code, Chapter 9 - Interior Finishes, or TCNA (Tile Council of North America) Handbook for ceramic tile installation over concrete
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