A skim coat is a thin layer of plaster, known as joint compound, that can be applied to walls to achieve a smooth and uniform surface. This finishing technique is particularly popular in the world of drywall finishing, where it’s employed to cover imperfections, smooth out textured surfaces, or prepare an uneven wall for painting or wallpapering.
Wallpaper can be a distinguishing feature in any room, but tastes and styles change over time, and what was once a beloved pattern can become a decorating obstacle. Removing wallpaper can be a tedious and time-consuming process, involving steaming and scraping to ensure the wall returns to a blank state. The challenge is even greater when dealing with older homes where multiple layers of wallpaper may have been applied over the years, sometimes directly on top of each other.
This brings us to the question: Can you skim coat over wallpaper?
The short answer:
Yes, you can skim coat over wallpaper. This technique can be a time-saving alternative to removing wallpaper, offering a way to smooth out the surface before painting.
First things first, check the state of the wallpaper. It should be securely glued to the wall with no signs of peeling or lifting. A problematic wallpaper can create issues later on. If the wallpaper is in good condition, the key to success lies in the preparation. The surface must be clean and free from dust, grease, or anything that would prevent the skim coat from adhering properly.
The next step is priming. An oil-based primer can seal the wallpaper, so the adhesive doesn’t loosen when it comes into contact with the wet joint compound. The priming phase is crucial; without it, you risk the wallpaper bubbling or peeling off.
Applying the skim coat is a skill that might require practice to perfect. It involves covering the whole wall evenly with a thin layer of joint compound. Skim coating can actually require multiple applications, each needing to dry and be sanded smooth before the next is applied.
After skim coating, the primed surface must dry and be sanded smooth before any painting begins. Once the walls are prepared, painting can proceed as usual, resulting in walls that look as if they were never wallpapered in the first place.
Preparing the Wallpaper
Preparing the wallpaper for skim coating is a critical part of the process to ensure the finished wall looks flawless. It revolves around making sure the wallpaper is impeccable and ready for the joint compound.
Start by cleaning the wallpaper. Wipe down the entire surface with a damp sponge or cloth to remove any dirt, oil, or residue. If the wallpaper is washable, a mild detergent can be used, but if it’s older or fragile, stick to just water. Let the surface dry completely before moving on to repairs.
Next, scrutinize the wallpaper for damage. Any loose or peeling sections must be re-adhered or, if necessary, cut away. Use wallpaper adhesive to fix loose edges or seams. Remember that the joint compound is only as reliable as the surface it adheres to, so take your time to ensure the wallpaper is firmly fixed to the wall.
Choosing the correct primer is vital. The primer creates a barrier between the wallpaper and the joint compound, preventing any moisture from seeping through and weakening the adhesive. An oil-based or shellac primer is recommended as both create a water-resistant seal. Carefully apply a coat of primer over the entire surface and let it dry according to the manufacturer’s instructions.
Once the primer is set and the wallpaper is sealed, you’ve laid the groundwork for a successful skim coat. The wall should now be clean, stable, and moisture-resistant, ready for the next step in the transformation process.
Materials for Skim Coating
The type of joint compound and the tools you use will affect the ease of application and the quality of the finish.
When it comes to the joint compound, there are two main types to consider:
1. All-purpose joint compound: This is a versatile choice that can be used for taping, coating, and finishing drywall seams as well as for skim coating. It has a good initial tack and is easy to sand.
2. Topping compound: Lighter than all-purpose joint compound, topping compound is designed for the final coat over drywall. It’s smooth, easy to spread, and creates a fine finish, making it an excellent option for skim coating over wallpaper.
Some prefer to mix their own setting-type joint compound, known as ‘hot mud’, for skim coating. These compounds come in different setting times, from 5 minutes to 90 minutes, giving you control over how quickly the compound dries.
For the application, you’ll need specific tools:
Drywall knives in various sizes: A 6-inch knife is suitable for tight areas or applying the initial coat of compound, while a 10-inch or 12-inch knife helps to smooth out the wider swaths for a flatter finish.
Mud pan: This is used to hold and carry joint compound as you work.
Sanding block or pole sander: Needed for smoothing out any ridges or bumps after the joint compound has dried.
Sandpaper: Fine-grit sandpaper is required for creating a smooth final surface.
Hawk: Some professionals may prefer using a hawk to hold the compound. This is a flat square plate with a handle underneath.
Trowel: In some cases, a trowel might be used for applying the skim coat, offering a larger blade surface than a knife.
Step-By-Step Guide to Skim Coating Over Wallpaper
Skim coating over wallpaper is a meticulous process that, when done correctly, will leave your walls looking smooth and refreshed. Follow this step-by-step guide to ensure a successful outcome.
Step 1: Load the Mud Pan*
Begin by filling your mud pan with joint compound. Scoop out a small amount onto the edge of your drywall knife or trowel.
Step 2: Apply the First Coat
Starting at the top of the wall, hold the knife or trowel at a slight angle and spread a thin layer of compound over the wallpaper. Work in small, manageable sections, moving in smooth, fluid motions to avoid creating air bubbles or ridges.
Step 3: Smooth it Out
After applying the compound, go back over the same section with your knife or trowel held at a higher angle to smooth out the compound. The goal is to fill in indentations without leaving excess compound on the wall’s surface.
Step 4: Let it Dry
Allow the first coat to dry completely. The drying time can vary depending on the humidity and temperature of the room but typically ranges from a few hours to overnight.
Step 5: Inspect and Sand
Once dry, inspect the wall for any imperfections. Use a light source held at an angle to the wall – this will help to highlight any bumps or ridges that need attention. Sand the dried compound using a sanding block or pole sander with fine-grit sandpaper, and then wipe the wall with a damp sponge to remove dust.
Step 6: Apply Additional Coats (if necessary)
If the wallpaper’s texture is still visible or if there are imperfections in the first layer, apply subsequent coats. Repeat the same process as the first coat, making sure each layer is smooth and free from excess compound. Allow ample drying time between coats and sand as needed.
Step 7: Final Sanding
After the final coat has dried, sand the wall one last time to achieve a super-smooth finish. Be gentle and thorough, checking for smoothness with your hand.
Step 8: Prime and Paint
Once satisfied with the smoothness, wipe down the wall with a damp sponge or tack cloth to remove all the dust. Then, apply a high-quality primer and let it dry before painting with the color of your choice.
Skim coating over wallpaper can be a practical solution for updating your walls without the labor-intensive stripping process. However, it requires careful preparation, the right materials, and a patient, methodical approach. By understanding the common challenges and addressing them head-on, your walls can be transformed into a smooth and inviting canvas for paint.
Can skim coating be applied over any type of wallpaper?
Skim coating can be applied over most types of wallpaper, but it is crucial that the wallpaper is firmly adhered to the wall and is in good condition. Vinyl, foil, fabric, or heavily textured wallpapers may not be suitable for skim coating and could require removal before proceeding.
Do I need to prime the wallpaper before skim coating?
Yes, priming the wallpaper is an essential step. It prevents the wallpaper from absorbing moisture from the joint compound and ensures better adhesion of the skim coat. Use an oil-based or shellac-based primer to seal the wallpaper effectively.
How many layers of skim coat do I need to apply?
The number of skim coat layers depends on the wall’s condition and the wallpaper’s texture. In many cases, one to three layers are sufficient to achieve a smooth surface, but each layer must be fully dried and sanded before applying the next.
How long does it take for the skim coat to dry?
Drying times for the skim coat can vary depending on environmental factors like humidity and temperature, as well as the thickness of the applied compound. It usually takes a few hours to overnight for each layer to dry completely. Always refer to the manufacturer’s guidelines for specific drying times.