How to Mix & Apply Stucco

by Emily Beach

Stucco is a material used for finishing exterior walls and surfaces. It is easy to mix and apply, and is surprisingly affordable and versatile. You can apply stucco over almost any surface, including masonry, wood, or siding. This material is especially useful for covering up damage in existing surfaces. While stucco is available in pre-mixed bags, its often much cheaper to buy the few required ingredients and mix your own batch.

Purchase your materials. Stucco is made up of Portland cement, hydrated lime, and sand mixed together with water. All of these materials are available at most home improvement stores. Use the guide on the bags of Portland cement to determine how many bags you need for your project.

Mix the stucco for your scratch coat. When applying stucco, you apply a scratch coat first. This provides a nice base for your finish coat. To mix your scratch coat, apply one part Portland cement, one part hydrated lime, and four parts sand. Blend these three ingredients together, then slowly add water until the mixture reaches the consistency of a thick paste.

Apply your scratch coat. Use your trowel to apply a 1/4" layer of stucco to the surface. Allow this coat to dry for about an hour, then use your plasterer's rake to etch lines all the way across the surface, approximately 1/8" deep. Give this coat 24 hours to dry completely.

Mix your finish coat. Mix one part Portland cement, one part hydrated lime, and two parts sand for this coat. Again, add water slowly until your mixture resembles a thick paste. Now use your trowel to apply another 1/4" coat. You can vary the pressure and angle of your trowel, or use it to dab stucco onto the wall. This will allow you to create interesting patterns and textures with your stucco.

Allow this coat 48 hours to dry. Mist the surface with water periodically to keep it moist. Stucco looks its best when it is allowed to dry slowly, with added moisture.

Items you will need

  • Portland cement
  • Hydrated lime
  • Sand
  • Water
  • Wheelbarrow or large bucket
  • Stirring stick
  • Trowel
  • Plasterer's rake

Tip

  • If you'd like to add color to your stucco, simply add colored pigments from your local home improvement store to your mixture.

Warning

  • Don't mix more stucco then you can apply in one hour. Stucco that is too dry when it is applied will crack and the appearance will not be as good as properly applied stucco.

About the Author

Emily Beach works in the commercial construction industry in Maryland. She received her LEED accreditation from the U.S. Green Building Council in 2008 and is in the process of working towards an Architectural Hardware Consultant certification from the Door and Hardware Institute. She received a bachelor's degree in economics and management from Goucher College in Towson, Maryland.