
Skim coating cement board is a process that involves applying a thin layer of material over the surface of the board to create a smooth and even finish. This technique is often used to prepare cement boards for painting, wallpapering, or other finishes. The process typically involves using a skim-coating compound, such as joint compound, drywall compound, or plaster, to fill in any imperfections and create a smooth surface. It is important to properly prepare the surface of the cement board before skim coating, which may include filling in screw holes and taping over the joints between boards. The specific process and materials used may vary depending on the manufacturer's recommendations and the intended use of the cement board.
Characteristics | Values |
---|---|
Materials | Cement board, thinset, fibreglass tape, stucco, concrete bonding agent, paint, cement screws, drywall primer, plaster, joint compound, cementitious skim coat and patching compound |
Tools | Trowel, paintbrush, tin snips |
Techniques | Skim coating, parging, taping, feathering, misting, sanding |
What You'll Learn
Use a skim coat of plaster for a harder surface
Skim Coating Cement Board with a Plaster Skim Coat
A skim coat of plaster can be used to finish a cement board and provide a harder surface. This method is suitable for small areas of cement board that will not be tiled, such as a board extending beyond a tiled area and abutting another surface.
Materials and Tools
- Setting-type joint compound (e.g., Durabond 90)
- Powder-type joint compound
- Fiberglass mesh tape
- Trowel
- Sandpaper (100-grit)
- Paintbrush
- Primer
- Paint
Steps
- Treat the joints and fasteners: Embed fiberglass mesh tape over the joints and treat fasteners with a setting-type joint compound applied in a conventional manner.
- Apply a skim coat: Flat trowel the setting-type joint compound over the board to cover fasteners and fill voids to create a smooth surface.
- Sand the surface: Once the skim coat has dried, lightly sand the surface with 100-grit sandpaper to remove any obvious ridges and create an even finish.
- Prime and paint: Apply a suitable primer to the surface of the cement board and then paint as desired.
Tips
- Consult the manufacturer's instructions for specific recommendations on finishing cement board.
- For larger areas, consider using a cementitious skim coat and patching compound, such as Micro Finish by Para-Chem, to achieve a smoother finish.
- Ensure that the screws used to install the cement board are corrosion-resistant and have ribbed "waferhead" or "truss head" designs.
By following these steps and tips, you can effectively skim coat a cement board with plaster to create a harder and more durable surface.
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Use drywall compound for a smooth finish
Skim coating with drywall compound is an excellent way to achieve a smooth, professional finish on interior walls and ceilings. It is a popular method for smoothing out textured walls, concealing flaws, and preparing surfaces for high-quality finishes. Here are the steps to follow to ensure a successful skim coating project using drywall compound.
Step 1: Wall Preparation
Start by removing any loose paint, wallpaper, or debris from the cement board. Fill in any holes or cracks with a suitable filler, such as spackling paste, and sand down any rough areas. Ensure the surface is clean and free of dust before applying primer. It is crucial to create a smooth base for the skim coat to adhere properly.
Step 2: Priming
Priming the wall before skim coating is an essential step. It seals the wall surface, creating a uniform substrate for the skim coat to adhere to. Choose a primer specifically designed for cement boards, as this will ensure proper adhesion and prevent issues like bubbling or peeling. Apply one to two thin coats of primer and let it dry thoroughly before proceeding to the next step.
Step 3: Mixing the Drywall Compound
When mixing the drywall compound, aim for a consistency that is easy to spread but not too runny. It should hold on to your knife without dripping but smooth out easily on the wall. Mix the compound in a bucket according to the manufacturer's instructions, adding slightly less water than specified at first. You can always add more water later if needed. This ensures a lump-free mixture.
Step 4: Applying the Skim Coat
There are several tools you can use to apply the skim coat, each giving slightly different results:
- Paint Roller: This method is great for beginners as it allows for easy and quick application over large areas. Roll the compound onto the wall in small sections, pressing the roller firmly to remove bubbles.
- Drywall Knife: A drywall knife offers more precision and control, especially around edges and corners. Use smooth, even strokes to apply a thin layer of compound and fill in imperfections.
- Texture Sprayer: This method is typically used by professionals as it requires specialized equipment. Fill the sprayer with the mixed compound and adjust the nozzle for the desired spray pattern. Hold the sprayer at a consistent distance from the wall and spray in controlled, overlapping patterns.
Step 5: Smoothing the Skim Coat
After applying the compound, use a skimming knife or trowel to smooth out the surface. Hold the knife at a slight angle to the wall and use smooth, even strokes. Apply light pressure, focusing on any ridges or excess compound left by the previous application method. Be careful not to gouge the wall with the corners of the knife.
Step 6: Drying and Sanding
Allow the skim coat to dry completely, which can take a few hours to overnight, depending on the temperature and humidity. Once dry, lightly sand the surface with fine-grit sandpaper to remove any ridges or bumps, creating an even smoother finish. Clean the dust off the wall before applying subsequent coats if needed.
Tips and Tricks
- For corners and edges, use a smaller knife to maintain control and precision.
- If you are using a roller, keep a damp rag and a mud pan handy to wipe off excess compound and clean the blade.
- To speed up drying time, use a space heater and a box fan, especially in humid conditions.
- If you are a beginner, practice mixing and applying the compound to a scrap piece of drywall to get a feel for the right consistency and technique.
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Use stucco for a raw plaster look
Stucco is a highly durable and versatile plaster coating that can be applied to cement boards to achieve a raw plaster look. It is made from a mixture of Portland cement, lime, sand, and water, which can be purchased pre-mixed or created from raw ingredients.
Stucco can be applied using a one-coat, two-coat, or three-coat method, depending on the desired finish and surface it is being applied to. The three-coat method, which includes a scratch coat, brown coat, and finish coat, is the most durable and traditional approach.
To achieve a raw plaster look, you can opt for a Mission or Santa Barbara stucco finish, which is left natural and unpainted. This type of finish showcases the beauty of the stucco in its raw state.
- Prepare the surface: Ensure that the cement board is clean and free of any debris. If there are any screw holes or imperfections, fill them with a suitable patching compound.
- Apply a bonding agent: Use a bonding agent or stucco wrap to ensure the plaster adheres properly to the cement board. This step is crucial for a smooth and durable finish.
- Apply the scratch coat: Using a trowel, apply a layer of stucco mixture to the cement board. This layer should be approximately 1/4" to 1/2" thick. Allow it to cure for up to 36 hours.
- Apply the brown coat: Once the scratch coat is dry, use a trowel to apply the second layer, also known as the brown coat. This layer provides a smooth surface for the final stucco finish. Allow it to dry thoroughly before proceeding.
- Apply the finish coat: After the brown coat is completely dry, apply the final layer of stucco with a trowel. Create the desired texture for the raw plaster look, such as a smooth or sand finish. Allow it to cure for another 36 hours.
- Optional painting: If desired, you can paint the stucco finish. It is recommended to use acrylic latex paint for this purpose.
By following these steps and choosing the appropriate finish, you can achieve a beautiful raw plaster look with stucco on your cement board. Remember to take your time and allow each layer of stucco to cure properly for the best results.
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Use a micrograin cementious floor patching compound for feathered edges
When skim coating cement board, using a micrograin cementitious floor patching compound for feathered edges is an effective approach. This method ensures a smooth and seamless finish, making it ideal for achieving a flawless appearance.
A micrograin cementitious floor patching compound is specifically designed to create a fine texture that can be easily sanded down to a feather edge. This product is perfect for filling in gaps, levelling surfaces, and creating a smooth base for further treatment. It is a versatile option that can be applied to various flooring materials, including concrete, wood, and tile.
To use a micrograin cementitious floor patching compound, start by cleaning the surface and removing any debris or contaminants. Follow the manufacturer's instructions for mixing the compound, usually by adding water to achieve a smooth and lump-free consistency. Apply the compound evenly to the desired area using a trowel or putty knife. For larger areas, self-levelling compounds can be poured and spread to achieve a flat finish.
Feathering the edges is a crucial step in achieving a seamless blend between the patched area and the surrounding floor. This process involves gently tapering the compound towards the edges, creating a gradual transition. Once the compound is dry, you can sand the surface for an even smoother finish if needed.
Using a micrograin cementitious floor patching compound offers several benefits. It provides a durable and long-lasting solution for repairing flaws in the floor. It is also cost-effective, user-friendly, and suitable for a wide range of applications, including residential, commercial, and industrial flooring projects.
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Use a cementitious skim coat and patching compound for smooth joints
To get a smooth finish on a cement board, you can use a cementitious skim coat and patching compound. This is a more expensive option, but it will give you a smooth, flat finish.
Firstly, you need to prepare the wall. If you have any large bumps or uneven areas, use a putty knife to scrape the wall and ensure you are starting with a clean wall. Then, prime the wall with a fast-drying, stain-sealing drywall primer. This will seal loose paper and promote better adhesion of the joint compound. Let the primer dry thoroughly before applying any joint compound.
Next, mix your cementitious skim coat and patching compound. For a large wall, you will need a large amount of joint compound, and you will want to mix it to a thick, pancake batter consistency. It is important to only use fresh, unopened compound, as even a tiny bit of dried-up compound can ruin your results.
Now you can apply the mixture to the wall. Use a heavy-nap roller to apply a thick layer of the mixture, making sure you can't see the wall through it. Work in small sections, as the compound will start to dry quickly.
The next step is to use a trowel to smooth the compound. Starting at the top of the section, drag the trowel down with gentle pressure to smooth the mixture flat to the wall. Overlap the next section by a few inches until you've smoothed the entire section. Don't worry about making it perfect, as you can fix any lines or uneven spots after it dries.
If you have very heavy texture, you might need to let the first coat dry and repeat the process. Once you are happy with the finish, let the compound dry completely. This could take around four hours, but it is recommended to leave it overnight.
Finally, you can smooth down any imperfections with a damp sponge. This will help you achieve a smooth wall without the dust of sanding. After this, make sure you use a good primer before painting or installing wallpaper.
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