Primer On Skim Coat Texture: When And Why You Need It

Skim coating is a process of applying a thin layer of material, such as joint compound, over a wall or ceiling to create a smooth finish. It is often done to remove texture from walls or ceilings, and it can be a time-consuming and labour-intensive process. While it is possible to skim coat without priming, priming the surface first is generally recommended as it can improve adhesion and help create a smoother finish. Priming also helps to seal the surface and prevent the skim coat from absorbing fluid, which could affect the final appearance. Additionally, priming can make it easier to spot imperfections in the skim coat, as they may be more visible over a white primer.

Priming before skim coating

There are different types of primers available, and the right primer for your project will depend on the condition of your walls. If your walls are in good condition, without water stains or torn drywall paper, you can use a latex primer. In the case of peeling paint, a primer specially formulated to prevent peeling is best.

If your walls have water stains or torn drywall paper, it is recommended to spot prime the damage with an oil-based primer before skim coating. Oil primer is messy and has a strong odour, but it is an excellent sealer for paint. Do not use a latex primer on torn drywall paper as it will cause the paper to bubble.

Once you have applied your skim coat, it is recommended to apply a second coat of primer before painting. This will ensure that your paint dries evenly and that you get the best finish.

Priming after skim coating

When to Prime

It is recommended to apply a primer coat before the first skim coat and another primer coat after the final skim coat. Painting directly over drywall compound without priming can cause issues with the finish when you paint. The primer acts as a surface sealer and base coat, improving adhesion and creating a smooth surface for the topcoat.

Choosing the Right Primer

For walls with water stains or torn drywall paper, an oil-based primer is recommended. Oil primer effectively seals the surface and prevents bubbling. However, it can be messy and has a strong odour. If you prefer a water-based option, Gardz or Rx-35 are recommended. These products seal the drywall and reduce bubbling. For walls in good condition without water stains or torn paper, a water-based latex primer can be used.

Application Techniques

When applying the primer, use a paint roller or a paint sprayer for larger areas to ensure even coverage. Pay attention to the directions on the primer, as some products may require multiple coats. Follow the manufacturer's instructions for drying time before proceeding to the next step.

Sanding and Final Preparations

After the final primer coat, lightly sand the surface to smooth out any imperfections. Use a fine-grit sandpaper or a sanding sponge, and always sand in the direction of the skim coat. Remove dust with a tack cloth or a vacuum attachment specifically designed for drywall dust. Fill in any remaining pinholes or imperfections with a small amount of joint compound.

Painting

Once the wall is primed and sanded, you can proceed with the final paint colour of your choice. Make sure to select a high-quality paint that is suitable for the surface and follow the manufacturer's instructions for application and drying time.

By following these steps and allowing adequate drying time between coats, you will achieve a professional-looking finish for your skim-coated walls or ceiling.

Skim coating tools

Skim coating is a process that can help smooth over rough or damaged walls. It involves applying a thin layer of joint compound or plaster to your walls. The tools required for skim coating include:

• A primer or sealer - this is necessary for preparing the walls and ensuring the joint compound adheres well.
• Joint compound - this can be mixed to the desired consistency and applied to the walls using a paint roller.
• Paint tray, mud pan, or bucket - these are used to contain the joint compound and facilitate the application process.
• Mixing attachment for a drill - this helps to mix the joint compound to a smooth, lump-free consistency.
• Thick-nap paint roller - this type of roller allows for a faster and more generous application of the joint compound to the walls.
• Magic Trowel - this is a rubber-bladed tool that helps to smooth out the joint compound and create an even finish. It is flexible and can be used in different directions for each coat.
• Sanding tools - light sanding may be required between coats or after the final coat to ensure a smooth finish. Options include a regular pole sander, a dust-free drywall sander, or wet sanding with a damp tiling sponge.
• Drop cloth or floor coverings - skim coating can be a messy process, so it is important to protect floors and furniture.
• Box fan - using a box fan can help reduce dust when sanding.
• Bright light - shining a light at an angle on the wall can help identify imperfections and ensure a thorough job.

Skim coating techniques

Skim coating is a technique used to smooth over rough or damaged walls. It involves applying a thin layer of mud or joint compound to the wall using a roller or trowel, and then smoothing it out with a squeegee knife or trowel. Here are some detailed steps on how to skim coat a wall:

Step 1: Prep the Walls

Before starting the skim coating process, it is important to prepare the walls properly. This includes cleaning the walls with a solvent or primer to remove any grease, dirt, or old paint. It is also crucial to patch any holes or tears in the wall and let the compound dry before proceeding.

Step 2: Roll on the First Coat

The first step in the skim coating process is to roll on a thin layer of all-purpose joint compound or mud onto the wall using a heavy-nap roller. Work in small sections, as you will need to smooth out the compound before it dries. Don't worry if you get cracking on the first coat, as this is normal.

Step 3: Trowel the First Coat

Once the first coat is rolled on, use a squeegee knife or trowel to smooth out the joint compound. Start at the top corner of the wall and pull the knife or trowel down in vertical passes, overlapping each pass until you finish the section. You may need to go over some areas multiple times to get a smooth finish.

Step 4: Let the First Coat Dry

After you have finished troweling the first coat, let it dry completely. You can speed up the drying process by using space heaters and fans, especially in humid conditions. Once the first coat is dry, use a putty knife to knock off any lumps or proud mud lines to avoid streaks in the next coat.

Step 5: Apply the Second Coat

For the second coat, change directions and trowel the joint compound at a right angle to the previous coat. This will help create a smoother finish. If you still see indentations or imperfections after the second coat dries, apply a third coat in the same manner.

Step 6: Sand the Wall

After the final coat has dried, use a pole sander with fine-grit sandpaper (120-grit or higher) to smooth out the wall and remove any remaining imperfections. If there are too many peaks and valleys, start with a coarser grit sandpaper and work your way up to a finer grit.

Skim coating can be a time-consuming and challenging process, especially for beginners. It may take multiple coats and a lot of sanding to achieve a smooth, matte finish. However, with patience and practice, it is possible to create smooth and professional-looking walls.

Skim coating and sanding

Skim coating is a process of smoothing over rough or damaged walls with a thin coat of mud, applied with a special squeegee knife. It is a good option if you want to get rid of the texture on your walls.

Before skim coating, it is important to prep the walls. Start by washing the walls with TSP (trisodium phosphate) or a TSP substitute to get rid of any grease, dirt, oil, or wax. Then, knock off any protrusions and prefill any large holes. It is recommended to prime the walls before skim coating, as primer will stick to old paint, and the mud will stick to the primer. However, if the brown underlayment on drywall is showing through, you will need to use a sealer like Gardz instead of a primer to prevent bubbling.

Once the walls are prepped, you can start the skim coating process. Mix all-purpose joint compound to a mayonnaise-like consistency and spread it on the walls with a heavy-nap roller. Work in small sections so that you can smooth out the compound before it dries. Use a squeegee knife to smooth out the compound, wiping the blade with a damp rag after every few strokes. You may need to go over some areas multiple times to get a smooth finish. Let the first coat dry and then apply a second coat in the opposite direction. If there are still indentations or imperfections, apply a third coat.

After the final coat is dry, you can start sanding. Use a pole sander with 120-grit sandpaper to sand the walls. If there are a lot of peaks and valleys, start with 100-grit sandpaper first. Once the walls are smooth, wipe them down with a damp cloth to remove any dust. Then, you can prime and paint the walls.

Frequently asked questions