Skim Coating Drywall Tape: Mastering The Art Of A Smooth Finish

how to skim coat drywall tape after sanding

Skim coating is a great way to smooth out or prepare worn or damaged walls. It is usually done to repair damage and improve appearance. Skim coating is also applied when retexturing after a drywall repair, touching up old or unsightly walls, and installing new drywall.

To skim coat your walls, you will need to prep the walls by covering up areas that will not be skim-coated. Shut off electrical circuits to outlets and light switches, and remove faceplates. Lay down drop cloths and tape them up to the wall baseboard. Mix the drywall compound in the bucket according to the mix ratio on the product instructions. Use a paint roller to apply an even layer of primer to your wall. Roll out the drywall compound onto a section of the wall. Smooth imperfections with a squeegee or taping knife. Continue working in slightly overlapping vertical sections until you finish the entire width of the wall. Apply additional coats as necessary. Once the final coating of the joint compound has dried, use sandpaper to smooth out any remaining imperfections.

Characteristics Values
Purpose Repair damaged walls and smooth down intentionally applied wall texture
Tools Squeegee and taping knives, sandpaper, paint stir sticks or stirring drill attachment, paint roller, mud pan, drywall knife, paint rolling screen for the bucket, primer, joint compound, drop cloths, painter's tape, vacuum attachment, spotlight, hand sander, drywall sanding kit, drywall primer, Glidden's Gripper Primer, Gardz, RX-35, sanding screens, putty knife, breathing mask, protective eyewear
Steps Prep the work area, mix the drywall compound, roll out the drywall compound, skim the first section, skim the rest of the sections, sand the dried skim coat, apply additional coats, sand remaining imperfections when dry

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Prep the walls

Before you start skim coating, you need to prep the walls. This will ensure that you get the smoothest finish possible. Here's what you need to do:

  • Cover up any areas that won't be skim-coated, such as windows and doors, with drop cloths and painter's tape.
  • Remove any wallpaper. This can be a tricky process, so be sure to take your time and use the right tools.
  • If there is any paint on the walls, clean it to remove any grime or flaking paint.
  • Repair any significant damage to the drywall, such as torn tape, dents, or holes.
  • Prime the wall. This will help the joint compound adhere properly and provide a smooth surface for future wall-painting projects. Use a paint roller to apply an even layer of primer to the wall, working from the outside in and covering the entire surface. Let it dry before moving on to the next step.
  • Thin out the joint compound to a consistency that is similar to pancake batter. You can use a mixer attachment on a drill to mix the joint compound, or mix it by hand.

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Mix the joint compound

Mixing the joint compound is a crucial step in skim coating drywall. The compound should be mixed to a thin consistency, similar to that of pancake batter or mayonnaise. This can be achieved by adding water to the compound in a bucket and stirring it with a paint stir stick or a stirring drill attachment. It is important to mix the compound thoroughly to avoid lumps and ensure a smooth finish. The consistency of the compound can be adjusted by adding more water or compound as needed. Once the desired consistency is achieved, the compound is ready to be applied to the wall using a paint roller or a sprayer.

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Apply the joint compound

The joint compound is the mud-like substance that will be applied to the wall to create a smooth finish. You can use either a pre-mixed joint compound or a powder that you mix with water. The pre-mixed compound will be the consistency of thick peanut butter, so you'll need to add a bit of water and mix it in carefully until you have a consistency close to pancake batter. If you're using a powder, mix the powder with the amount of water recommended on the container, which should give you a thick peanut butter consistency. Then, slowly add more water and mix until you reach the pancake batter consistency.

You'll want to use a large bucket for mixing, as it can get messy, and a mixer attachment on a drill to ensure the compound is thoroughly mixed.

Pour the mixed joint compound into a paint tray and gently dip your paint roller into the tray until it's covered in a thin, even layer of the compound. Then, apply it to the walls in vertical sections, working from the ceiling to the floor. Each section should be about three to five feet wide.

Once you've finished one section, use a squeegee or taping knife to smooth out the compound. Start at the top of the wall and work downward, using gentle pressure to drag the tool downward and smooth the wall. Any excess compound in the high spots should fill in the low spots. Then, work from the floor upward, again using gentle pressure to drag the tool and smooth the wall.

As you smooth the compound, you may end up with some excess on your tool. If so, use a towel to wipe it clean.

After finishing one section, use a spotlight to check for areas you may have missed or areas with too much compound. Shining the spotlight from the side can help reveal imperfections. Fix any issues with the squeegee or taping knife, or, if the compound is becoming too thick as it dries, spray the area with water to temporarily soften it.

Try to make the section as smooth as possible, keeping in mind that you can sand later. Continue working in slightly overlapping vertical sections until you've finished the entire width of the wall.

Apply Additional Coats

After the wall has dried, inspect it again with a spotlight. The thinner layer used in skim coating means it may dry within 30 minutes to four hours. If it's not as smooth as you'd like, consider adding a second skim coat of the compound. Follow the same process as before, but this time, use the squeegee or taping knife at a right angle to the previous coat. For example, if you dragged the tool vertically for the first coat, drag it horizontally for the second coat. Alternate the direction with each subsequent coat.

Sand Remaining Imperfections

Once the final coat of the joint compound has dried, use sandpaper to smooth out any remaining imperfections. Opt for a hand sander over an electric one to avoid removing too much compound and creating more imperfections.

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Smooth the joint compound

Now that you've sanded your drywall, it's time to smooth the joint compound. This is a thin layer of drywall joint compound (also known as mud) that gives walls a glass-smooth finish. It's also called plastering a wall, though you are using drywall joint compound, not plaster. The purpose of skim coating is to repair damaged walls and smooth down intentionally applied wall texture. You can also cover a popcorn ceiling using skim coating.

Skim coating is an easy, low-mess alternative to chipping away the texture material. It costs less than alternatives like replacing drywall, removing texture, or adding paneling. But it's labourous, and if you're a beginner, it helps to know that you need patience to get the skimming just right for that coveted seamless look.

Preparation

Before you start skim coating, you'll need to prime the wall. Priming will also seal any loose paper on the drywall that you're covering. Apply one to two thin coats of appropriate primer to the wall and wait until it is thoroughly dry to begin skimming.

Mix the joint compound

Use a light-body drywall compound. Since the compound serves almost no structural purpose, a heavy-body compound is not necessary. Plus, lightweight mud is easier to sand smooth.

Mix the drywall compound in the bucket according to the mix ratio on the product instructions. Often, it's better to short the water slightly to produce a heavier, stickier product. This gives the skim coat greater strength, plus it's cleaner to apply. Mix to a stiff, yogurt-like consistency.

When mixing drywall compound, determine the amount of water needed according to the manufacturer's instructions on the product. Put slightly less water than needed in a mixing container or bucket and add compound to the water. After mixing, add the remaining water if needed. Adding the compound to the water is better for achieving a lump-free mixture than adding all the water to the compound at once.

Apply the joint compound

Roll out a section about 2 feet wide by 8 feet high. Press the roller firmly into the wall to force out bubbles. Working time depends on the amount of drywall compound deposited on the wall, room temperature, and airflow. It's always better to maintain smaller working zones so that the drywall compound does not dry up on you.

Be sure to keep the drywall compound consistent across the surface. Even though the drywall compound does get scraped off, inconsistent compound dries at different rates, so the process will be easier if you do a consistent application.

Skim out the drywall compound with a 12-inch knife. Scrape either upward or downward in columns, applying slightly more pressure to the left side of the knife than the right. This eases out imperfections on the left side but leaves a low ridge on the right side.

Do not exert full force with the knife because you will end up scraping off too much drywall compound, and you risk gouging the wall with the corners of the drywall knife. Deposit excess in the tray.

Make a second pass adjacent to the first column. Again, favor pressure on the left side. This eliminates the ridge on the left. Overlapping ensures that most of the ridges are taken care of by the drywall knife. This leaves less drywall sanding for later.

Sand the dried skim coat

Allow the skim coat to dry. It should dry within an hour or two.

Finish with a light sanding with fine-grit drywall sandpaper.

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Sand the dried skim coat

Sanding the dried skim coat is the next step after skim coating. It is important to wear protective gear like a breathing mask, eyewear, and maybe a hat to protect yourself from the dust. You can use a hand sander or a sanding kit for this step. Start with coarse-grit sandpaper and work your way to a finer grit. If you are doing skim coats in multiple rooms, consider investing in sanding screens instead of traditional sandpaper as they last longer and do not clog. They also come in 220-grit, which will give your walls a smooth finish.

You can also use a drywall hand sander kit, which usually comes with a connection hose that can be hooked up to a shop vac, eliminating about 90-95% of the dust. It is also recommended to use a flashlight to check for any missed spots, scratches, and pockmarks on the wall. A good lighting setup will help you identify any areas that need to be filled in with extra mud or sanded down.

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Frequently asked questions

Skim coating is a thin layer of drywall joint compound (also known as mud) that gives walls a glass-smooth finish. It's also called plastering a wall though you are using drywall joint compound, not plaster.

You don't have to skim coat new drywall. However, if you want to paint on almost perfectly smooth drywall, skim coating is money well spent.

Most people will skim coat the entire wall unless unusual circumstances exist. If you have a couple of areas of a wall that have a bad finish, you can apply a layer of skim coat on those areas to smooth them, improving the look.

You can skim coat over almost any type of textured wall to create a smooth finish, if desired. However, the skim coating process differs when going on textured versus non-textured walls. For the textured wall, you need to use a thicker layer of mud that has a consistency similar to smooth peanut butter to cover the texture. For the non-textured wall, you can apply a thin layer of mud with a paint roller, using mud with a consistency like pancake batter.

You can apply skim coat over a painted wall, as long as you follow a few key steps. Start by cleaning the wall thoroughly, removing any dust or greasy spots. If you’re going over glossy paint, rough it up a bit with fine-grit sandpaper, so the mud will adhere better. You also should use a drywall primer over the top, whether you have glossy or flat paint, to help with adherence. Once everything dries, you can start the skim coating process.

You can skim coat over wallpaper, but you must follow a few techniques. Start by removing any loose segments of wallpaper. The less wallpaper you have to remove, the faster the job occurs, but loose wallpaper must go. Additionally, it is difficult to skim coat over highly textured wallpaper, so you may need to remove all of it in a case like this. Apply a stain-sealing primer over the wallpaper. This prevents the wallpaper from absorbing the mud. After the primer dries, you are ready to start the skim coating process.

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