Which characteristic makes cementitious backer units less suitable in weight-sensitive applications?

• A. Their rigidity
• B. Their weight
• C. Their moisture resistance
• D. Their cost

Answer: (B)

In weight-sensitive installations, the amount of dead load a substrate adds to the structure is the key factor. Cementitious backer units are relatively heavy, so they substantially increase the overall weight that the structure must bear. That extra heft can constrain where they can be used, complicate handling and installation, and may require stronger framing or support. Their rigidity and moisture resistance are advantageous traits for tile substrates, providing solid support and durability, which is why they’re often chosen in other contexts. Cost can influence material choice, but when weight is a constraint, the heavy weight is the main drawback. So the characteristic that makes them less suitable in weight-sensitive applications is their weight.