Which statement correctly reflects the exterior cement-to-sand mix by parts?

• A. 3:1
• B. 4:1
• C. 5:1
• D. 7:1

Answer: (A)

For exterior plaster and stucco, you want a mix that balances binding strength with workability and durability in weathered conditions. The standard approach is three parts sand to one part cement. This sand-rich mixture provides enough cement to bind the surface securely while the sand gives bulk, texture, and porosity to allow moisture to escape and to reduce cracking from shrinkage. If you push more cement into the mix, it becomes stiffer, sets harder, and is more prone to cracking and costly, while if you reduce cement and add more sand, the coating can become weak and prone to crumbling. So, the three-to-one sand-to-cement balance is the practical, commonly used exterior mix.