Stucco is a material made of Portland cement plaster that is applied to an interior or exterior building surface. It is a strong, hard, fire-resistant material that is breathable allowing moisture vapor to escape. Stucco buildings are commonly found in warmer climates and locations like Florida and Texas. If you live in these areas a silane/siloxane based sealer is going to be your best option. A silane/siloxane based sealer is a water repellent that will penetrate and cause water to bead off of the surface.
The best sealer for stucco is the Siloxa-Tek 8500. The Siloxa-Tek 8500 is an excellent product for sealing stucco since it is also a salt repellent sealer, meaning if you live in a tropical environment with salts in the air the sealer will protect from cracking, spalling and pitting. The Siloxa-Tek 8500 will last up to 10 years before another application is required and since it is a natural finish product the sealer will never wear away, fade, yellow, crack or peel. The Siloxa-Tek 8500 must be applied to stucco that has never been painted; however, after applying the Siloxa-Tek 8500 you can paint over the sealer with an oil or enamel based paint.