A drawback of sand lime mortar is that it is what?

• A. It is flexible
• B. It is water soluble
• C. It dries fast
• D. It is inexpensive

Answer: (B)

Sand lime mortar uses lime as the binder, and lime is readily dissolved by water. Because of this, the mortar can be washed out or leached when exposed to moisture, leading to loss of material, reduced strength, and efflorescence. That vulnerability to water is the primary drawback, especially in areas exposed to rain or firefighting water, where the mortar can deteriorate over time. The other statements don’t reflect the common limiting characteristic of sand lime mortar: it doesn’t dry quickly—lime mortars cure slowly—and the cost isn’t the defining drawback in typical use.