Stucco is a beautiful exterior finish that can be applied over wood sheathing, masonry, and brick. It requires a base coat, brown coat and color coat. Mix the brown coat made from 1 part cement material and 3 to 5 parts plaster sand. Trowel and float it to produce a thickness of about 3/8 inch. It may also contain pigment to add color. Click on Stucco Repair Philadelphia for more details.
Lathing is an essential step in new stucco projects. It protects the underlying surface from moisture damage and it helps the stucco adhere to the wall. Depending on the project, lathing can be made from wood, expanded metal, or woven wire cloth. Lathing also comes in a variety of different sizes, shapes and gauges.
Generally, a weep screed and an asphalt coated waterproofing paper are installed on the substrate before lathing. The weep screeds are designed to direct water and vapor away from the structure. This is important because moisture in the walls can cause rot and other issues in the framing.
Once the weep screeds and paper are in place, metal lath or a non-metallic alternative is attached to the structure. The lath is fastened with galvanized nails, dog ear nails or staples. Ideally, the lath should be positioned in an even and consistent manner. If the lath is not positioned properly, it can allow moisture to seep behind the stucco and create cracks or other problems.
Lath can be either metal or a wood material like cypress or fir. It can be furred or unfurred. If the lath is not furred, it should have tongues or hooks that grab plaster when it is applied. Unfurred lath is typically used for ceilings and overhangs, while a metal or wood furring is usually used for walls.
It is critical that the surface of the lath be free of contamination, especially paint or sealer. Otherwise, good bonding can be inhibited. This can cause the stucco to fail, resulting in a delamination of the layer. Ideally, the surface should be sanded and clean prior to installing the lathing.
If the lathing is to be made from a wood product, it should be nailed or screwed to the framing members. The wood must be treated and pre-painted to ensure that it will not rot or deteriorate before the stucco is installed. If the lath is to be made from metal, it must be galvanized to protect it from rusting.
It is also recommended that expansion joints be installed along the length of the wall and in corners. These joints are believed to relieve stress on the stucco, minimizing cracking. Other items that may be added to the lathing process include milcore and plaster stops, corner aids and arch aids as needed.
When installing stucco, a plasterer applies a base layer called the scratch coat. The scratch coat is a mixture of sand and cement that bonds to the lath. It is then scraped in a grid pattern with a tool called a scratcher. Then the mixture is left to cure for about 48 hours.
The scratch coat is important because it helps to protect the surface from damage. It is also used to prevent water from penetrating the wall and causing issues with mold and wood rot. To keep the scratch coat moist, a plasterer sprays it with water every morning and evening. This is an important step in the process because it can help to make sure that the scratch coat will adhere properly.
Once the scratch coat has cured, it is time to apply the brown coat. The brown coat is a mixture of sand, cement, and fibers. This layer is a little thicker than the scratch coat and it can be used to add a decorative touch to the wall. The brown coat can be sprayed or brushed on to the surface of the wall. Once the brown coat is applied, it needs to be cured for about 48 hours.
During this time, the plasterer will use a tool called a darby to make sure that the brown coat is evenly spread out across the surface of the wall. Then, he or she will use a float to smooth out the surface of the brown coat. This can be done by hand or with a machine.
In addition to the brown coat, the plasterer will also use a trowel to apply a thin layer of stucco on top of the brown coat. This can be done to help add texture and to make the finish look more authentic. After the trowel work is completed, the brown coat will need to be cured again for about 48 hours.
If you are interested in adding a stucco exterior to your home, you should contact a professional stucco contractor for an estimate. There are many factors that can affect the timeline of the project, such as weather and availability of materials. Also, it is important to keep in mind that during the COVID-19 crisis there have been some material shortages that can impact your project.
Stucco is a plaster that protects and beautifies building exteriors. A long-standing traditional material for home construction, stucco is popular for its durability and design flexibility. A variety of colors and textures can be used to create different looks. However, poor installation or weather conditions can cause problems. Some problems can be repaired, while others require the entire stucco surface to be removed and replaced. In either case, these problems can be very costly.
Stucco can bond directly to masonry surfaces, but on sheathed walls the stucco must be attached mechanically. For this, contractors use expanded metal lath or “stucco netting,” a 17- or 18-gauge galvanized wire woven into a hexagonal mesh that looks a bit like chicken wire. The lath must be installed correctly to provide proper support for the stucco and prevent water intrusion. Ideally, the lath should be run perpendicular to the studs and all vertical and horizontal laps should be staggered. Laps that are too tight can rip away the sheathing and allow water to leak behind the stucco.
The scratch coat, which is the first layer of stucco applied to the wall, consists of a mixture of sand, cement, and reinforcing fibers. The scratch coat is then scraped horizontally to expose the sheathing and create a rough texture that allows the brown coat to adhere to it better.
Generally, the scratch coat should be 3/8 inch thick and moisture-cured for 48 hours before the brown coat goes on. This curing period minimizes cracking and helps the brown coat adhere well. During this time, it is important to mist or fog the stucco as needed to keep it moist.
The brown coat is made of the same materials as the scratch coat, except it is smoother and contains a colorant to add a final color to the stucco. It is sometimes referred to as the ‘base coat’ because it acts as the primary cladding layer and provides the substrate for an architectural finish. The base coat also controls the permeability of the system. Poor curing of the base coat can cause problems that affect both the cladding and the finish.
During the final stages of stucco installation, contractors finish the surface. This decorative finish coat is usually white, but other colors are available. It is composed of cement materials and sand, plus pigment to create the desired color. The finish is troweled or floated onto the scratch and brown coats, creating a 1/8 inch (3 mm) layer. The thickness of this coat determines the texture of your finished stucco wall.
The finish coat can also contain aggregate to give it a textured look, which is popular with customers. Some contractors use a texture roller instead of troweling to achieve a textured finish. The last step is to water the finish, similar to how you mist or fog the scratch and brown coats, to keep it moist while it cures.
While stucco is a very durable material, it does require regular maintenance to prevent excessive moisture penetration. Water penetration can damage the coating from between layers, causing efflorescence and staining, or from within the substrate, which can lead to bulging and ultimately collapse of the structure. Excessive moisture also leads to fungus, algae and biological growth that can stain or discolor the surface.
Stucco installation is a labor-intensive process that isn’t suited to DIY. It requires a skill set few homeowners would have, and it requires the right tools and equipment. The high cost of these items can also discourage some homeowners from pursuing the project.
A certain amount of shrinkage cracking is inevitable in any stucco exterior, particularly over wood-frame construction. However, these cracks can be minimized by using sheathing with adequate racking strength, and by ensuring that the scratch and brown coats are thick enough to hide them. Small shrinkage cracks are considered part of the character of traditional stucco, but a lot of them indicates substandard work.
Some stucco systems are more resilient than others, including insulating EIFS (Exterior Insulation and Finish System) assemblies that feature foam boards. These systems have a more complicated and expensive installation process, but they also resist moisture better than traditional stucco.