Traditional stucco is a beautiful and easy to maintain exterior finish. It is not to be confused with an exterior foam insulation system (E.F.I.S.) which has with an acrylic finish and can mimic the look of traditional cement stucco. True stucco consists of lath and a three coat cement application. The bags of cement and their mixes are heavy, making the application of stucco a strenuous job. Unless you are physically up to it, you will want to hire an experienced contractor to apply the stucco for you (see choosing a contractor). Either way, listed below is “tried and true” instructions for a plaster stucco mix and its application. Whether you decide to do it yourself or hire someone to do it for you, reading through this page will give you the basics of conventional stucco application.
The first step in stucco application is the lathing. The proper installation of lath, the foundation of stucco, is important to achieving a great finish. The way you lath is dependent on your substrate. On a typical wood framed house with plywood siding, you would tack or nail on one layer of black weather resistant stucco paper (60 min Super Jumbo tex) to hold it in place before the trim and the stucco wire mesh is applied. Make sure the flashing is in place at the top of the windows and doors before laying your paper and trim. This step is very important to the integrity of the finished stucco as water seepage behind the stucco can cause damage. After the paper has been applied, you apply the trim around the windows and doors so that you will have a gauge to follow for leveling of the mud during application. The stucco mesh (17 gauge self furring) is then hung over the paper using galvanized roofing nails or staples every eight inches to attach it to studs securely. Usually, stucco wire is marked every eight inches to make it more convenient for you to attach it. What about other types of substrate? If you have a steel stud building with plywood siding, you would apply the lath in the same manner, except that you would use screws instead of nailing. Another, more expensive, option for a steel stud building is to use sheets of metal rib lath instead of paper and wire over plywood. However, it is more difficult to apply the first coat of cement (scratch coat) over rib lath if you are inexperienced. Finally, the lath for badly weathered brick or concrete masonry surfaces can vary greatly depending on the mechanical bonding (ability for the stucco to adhere to substrate because of surface irregularities) available on the substrate. You may be able to apply stucco directly on this type of surface, but you might also need to nail on wire or sheets of metal lath using concrete nails.
After the building has been lathed properly, you are ready for your first coat of stucco. This is known as the scratch coat. The mix for one batch of stucco (which can be used for the scratch and brown coat both) is one 94 pound bag of Portland cement (type1 or type2), one 70 pound bag masonry cement, and 32 shovels (a regular square shovel) of clean mortar sand. To the mix add enough clean water to make it a consistency that is good for hand spreading. The first coat should be applied to about a 3/8” thickness. As the mortar for the first coat starts to firm, use a scratcher(see tools of the trade) to inscribe lines on the mortar. The grooved lines allow the brown coat to adhere and bond to the scratch coat. When you are done applying the mud for the scratch coat, you need to clean your tools and mixer with water as any mud left on them will harden and ruin them. Once the scratch coat is complete, allow it to dry for 1-2 days before applying the brown coat.
After waiting a day or two, a second batch of stucco should be mixed. This is known as the brown coat. The brown coat is applied to about a 3/8” thickness over the scratch coat. Level this coat with a rod and bring the surface to a true plane. The trim can be used as a gauge for leveling. The brown coat must be made to look nice because it will determine the final look of the finish. It is best to wait a minimum of 2 weeks after the application of the brown coat in order to allow any shrinkage to occur before the final finish texture is applied. This waiting period allows the brown coat to cure (and sometimes crack) which will actually help to avoid later cracking in the finish.
The final stucco coat, usually applied by hand, comes in many different textures and finishes. Therefore, you may want to look at the varying textures of buildings in your area in order to get a better idea of what you will want. If you decide to do it yourself, you will want to practice on boards before applying. There are also several choices of finish type. For example, you can apply a grey cement conventional finish (one 94 pound bag of Portland cement, 2 bags lime, and 3 bags of silica sand (20/30 grit). This type of finish is usually painted with a primer and top coat (preferably acrylic based) once it is completely dry. Another option is to apply a factory prepared finish coat such as an acrylic based finish coat, like Dryvit, which comes in five gallon buckets and has polymers and color in the mix already. The overall texture and color will be more uniform with an acrylic based finish. A final option is to add color (ex. La Habra color) to the cement mix itself. Although you can avoid painting with this type of finish, it is hard to maintain uniformity in color during application (usually leading to color variations in the finish). Stucco is known for its long lasting and beautiful finish, but to keep it that way, you will need to check and maintain it. For example, caulking around the windows and doors will need to be checked and maintained on a yearly basis to ensure that no water gets behind the stucco. It is also recommended that you walk around your home once a year to check for problem areas that need repair (though unlikely if stucco is done correctly and maintained). By doing this, you can save yourself a lot of money because a small patch can easily, and inexpensively, be fixed avoiding larger more expensive problems down the road. Finally, stucco can be washed and scrubbed down with soap and water to eliminate dirt and algae and make it look new, or it can be cleaned and repainted. If all phases in the stucco application are done properly and the finish is maintained afterwards, the stucco will last and look great for years and years.